Riolu can only be found on Route 22, and with a 5% encounter rate, both in regular grass and the yellow flowers. Lucario can be received as a gift Pokémon from Korrina in the Tower of Mastery; it holds a Lucarionite and will always be Hasty.
A major MVP of plenty of runs past, and plenty more to come. While unavailable in most games, Lucario is a force to be reckoned with wherever it goes; its incredible movepool and fantastic offensive stats make it immensely versatile in any team. In addition to that, while its defenses are only average, its part-Steel typing offers it a resistance to many types, some of which are also really common or lacking in counters; Lucario's effective bulk only really falls short against special moves it has a weakness against, which is really saying something about its power. The Mega Evolution addition has worked fantastically to further strengthen the already amazing qualities it has, even more so because it is the earliest Mega Evolvable Pokémon in the whole game. Catching it as Riolu is, of course, less advantageous in some aspects, but it also has its perks: being a friendship evolution, the player has total control over when to evolve it, and with enough patience Lucario could be evolved as early as before the first gym, by roller skating around to boost Riolu's friendship levels. Even if Riolu is kept unevolved until after Viola, with all the walking around there is to do in Kalos, it should naturally evolve long before the second gym, at which point it already wrecks everything in sight, with or without Mega Evolution.
Gym #1 - Viola (Santalune City, Bug-type): Riolu's Quick Attack is better than Surskit's Bubble and retains priority, so Riolu can win with or without Speed drops; Surskit will averagely be 4HKOed. Riolu cannot fight against Vivillon, instead, whose Tackle is stronger than Riolu's Quick Attack by far, and Vivillon also knows Harden as well as Infestation, which can add to the health chipped away from Riolu every turn. Lucario can defeat Vivillon with Quick Attack without much of an issue, as it will outdamage Vivillon's Tackle even if its Defense is maxed out.
Professor Sycamore (Lumiose City): Riolu's Quick Attack is slightly stronger than Bulbasaur's Vine Whip and Charmander's Ember, and KOs both in four to five hits; however, both have Growl, and may force Riolu to eventually switch out, especially Charmander which also sports Smokescreen. Squirtle starts off stronger with Bubble and Riolu is unlikely to defeat it, but can weaken it before switching out. Lucario has a better matchup, and can also defeat Squirtle without problems.
Tierno (Route 5): Corphish should be avoided by any Riolu that does not already know Force Palm, the only move that is likely to 2HKO it, or 3HKO at worst, before the Swords Dance spam becomes dangerous. Lucario 2HKOs with either Force Palm or Power-Up Punch, but can also wear Corphish down with just Quick Attack if it still knows no STAB moves, since its Vice Grip is resisted and deals low damage.
Tierno and Trevor (Route 7, tag battle with rival): Riolu's Force Palm is a 2HKO against Pikachu and a 3HKO against Corphish, but Flabébé is a problem, as it 2-3HKOs with Fairy Wind and the damage may stack with Pikachu's Thunder Shock. It is advised to beat Flabébé with another Pokémon first, and then have Riolu enter the battlefield to finish off the ones that are still standing. Lucario is exempt from this issue, since its dual typing is neutral to Fairy and Force Palm can 3HKO Flabébé despite the resistance.
Gym #2 - Grant (Cyllage City, Rock-type): Lucario should be fully evolved at this point. It can OHKO Amaura with either Power-Up Punch or Force Palm, and if it knows both moves and does use Power-Up Punch against Amaura, it will also OHKO Tyrunt with Force Palm the following turn; otherwise, both Force Palm and Power-Up Punch will 2HKO (Power-Up Punch cannot OHKO even after the Attack boost obtained against Amaura).
Korrina (Geosenge Town, Fighting-type): The match is perfectly mirrored. Lucario can win with two Power-Up Punches against the first of Korrina's Lucario, then using Force Palm against the second. Power-Up Punch may OHKO the second as well, if Lucario does not know Force Palm, but this is not guaranteed; if it comes down to it, Lucario can take two unboosted Power-Up Punches, each from a different enemy Lucario. Specimens with a Speed-lowering nature must run their calculations before fighting Korrina, as being outsped means defeat in this battle.
Rival (Tower of Mastery): Meowstic is 2HKOed by Shadow Claw; Inner Focus Lucario will be at an advantage in this matchup, as Meowstic often leads with Fake Out. Absol is best taken down with two Power-Up Punches, as Force Palm is highly unlikely to OHKO; alternatively, Swords Dance and Force Palm accomplish the same. After reaching +2 in Attack, Lucario can 2HKO Quilladin and Frogadier (the latter is not a guarantee, but highly likely) with Force Palm or more Power-Up Punches, and OHKO Braixen with Dig.
Gym #3 - Korrina (Shalour City, Fighting-type): Lucario can handle this matchup if it manages to 2HKO Mienfoo with Power-Up Punch. In that case, Machoke will also be 2HKOed by the same move, and Lucario can take a Power-Up Punch from both Pokémon without needing to heal. Unfortunately, Hawlucha's Flying Press and higher Speed will then put a stop to Lucario's sweep, as Hawlucha is impossible to OHKO even if Lucario's Attack is at +4.
Korrina (Tower of Mastery, Fighting-type): This matchup can only be fought by Korrina's future gift Lucario, which is always Hasty. As Mega Lucario, Power-Up Punch will 2HKO and Lucario's nature guarantees it will outspeed, though Lucario will also fall to a critical Power-Up Punch from the enemy.
Rival (Coumarine City): Lucario can 2HKO Meowstic with Shadow Claw; a Lucario with Inner Focus will also bypass the Fake Out turn, should Meowstic use the move. Absol is 2HKOed by Power-Up Punch, or by Swords Dance and then Low Sweep; at +2 in Attack, Quilladin is 2HKOed and Frogadier is OHKOed by Low Sweep, whereas Braixen is OHKOed by Dig. Quilladin may also be OHKOed if Lucario knows Poison Jab. Mega Evolution is not needed in this fight.
Gym #4 - Ramos (Coumarine City, Grass-type): A regular Lucario can 2HKO Jumpluff by setting up a Swords Dance and then using Poison Jab; it should then use an additional Swords Dance against Weepinbell, which guarantees the OHKO against it and Gogoat. Mega Lucario needs only one Swords Dance (or its equivalent) to OHKO all of Ramos' team with Poison Jab.
Aliana (Kalos Power Plant): A regular Lucario 2HKOs Mightyena with two Power-Up Punches or a Swords Dance and then Low Sweep, but does risk Mightyena using Swagger, which is doubly dangerous if confusion is not healed, since Lucario's Attack boosts will have reached +3 or +4 at that point. Mega Lucario can simply OHKO with Low Sweep instead.
Gym #5 - Clemont (Lumiose City, Electric-type): A regular Lucario needs Swords Dance, Low Sweep, Bone Rush if possible, and another move of choice to properly fight against Clemont. Swords Dance is the recommended starter against Emolga; if Emolga stays in and uses Aerial Ace or Quick Attack, Lucario can then KO it with a strong move of choice - Return is recommended, but Rock Tomb also works - or, if it switches out, it can OHKO Magneton with Bone Rush or Heliolisk with Low Sweep. Lucario can take a Thunderbolt from Heliolisk on the first turn, since Heliolisk is likely to outspeed, but may then need to be healed against Emolga if it also outspeeds Lucario. Mega Lucario can OHKO Heliolisk without Attack boosts, but is not guaranteed to OHKO Magneton with Bone Rush if it only hits twice; the upside is that Mega Lucario's Speed is higher than any of Clemont's Pokémon's, thus not needing to worry about Heliolisk's Thunderbolt. Do note that Magneton's Sturdy is the reason why Bone Rush is required over Dig.
Rival (Route 14): A regular Lucario's Shadow Claw still 2HKOs Meowstic, whose Psychic cannot do the same, and Absol is either 2HKOed by Power-Up Punch or 1-2HKOed by Low Sweep (the former is recommended). If Lucario has a previous +2 Attack setup from Power-Up Punch, it can OHKO Greninja with Low Sweep and 2HKO Chesnaught with Poison Jab; it must not fight Delphox, whose Mystical Fire is a 2HKO, as Delphox is also faster and Shadow Claw is not a guaranteed OHKO against it anywhere below +3 Attack. Mega Lucario can 2HKO Meowstic with a combination of Power-Up Punch and Shadow Claw, OHKO Absol with another Power-Up Punch, and then OHKO Greninja with any Fighting STAB or 2HKO Chesnaught with Poison Jab, as well as outspeed and OHKO Delphox with Shadow Claw.
Gym #6 - Valerie (Laverre City, Fairy-type): Mawile only has two Dark-type offensive moves and Iron Defense, and makes perfect setup material for Lucario. If Iron Defense is never used, Power-Up Punch will 3HKO, securing the Poison Jab OHKO against Mr. Mime and Sylveon (which is already guaranteed at +1 Attack for the former, and +2 for the latter). Mega Evolution is not needed.
Celosia and Bryony (Poké Ball Factory, tag battle with rival): Lucario should start off by OHKOing Liepard with Low Sweep, removing one source of damage from the battlefield; then, it can 3HKO Manectric with the same move, or Power-Up Punch, or a Swords Dance and two of its Fighting STABs. Mega Lucario can 2HKO Manectric without any setups. Alternatively, regular Lucario can also 2HKO Manectric, but with Aura Sphere instead.
Mable (Frost Cavern): Both Lucario and Mega Lucario OHKO Houndoom with Close Combat, though a regular one may be outsped unless its nature favours Speed. Fire Fang only 2HKOs, at any rate; only critical hits can kill regular Lucario, and cannot kill Mega Lucario.
Rival (Anistar City): Meowstic is yet again 2HKOed by regular Lucario's Shadow Claw, and Absol is OHKOed by either Close Combat or Aura Sphere. If the rival's starter is Chesnaught, Lucario should set up with two Swords Dances against Absol before OHKOing it, as they allow Lucario to also OHKO Vaporeon and Chesnaught; if the rival's starter is Greninja, only one Swords Dance is needed, but Lucario must KO Flareon with Dig and not Close Combat, to keep its Defense drops to -1 and thus live even a five-hit Water Shuriken from Greninja before landing the KO. If the rival's starter is Delphox, Lucario is not in luck: Jolteon and Delphox will outspeed, and Lucario can only take Discharge, as it is highly likely to be one-shot by Flamethrower and Delphox may outspeed it. Mega Lucario, in addition to beating two of the three possible teams with the same strategy, can OHKO both Jolteon and Delphox - though only Delphox will get outsped by it - with Dig, after using one Swords Dance against Absol.
Gym #7 - Olympia (Anistar City, Psychic-type): A regular Lucario can win against Olympia, but must take chances doing so. Leading with Swords Dance is good if Lucario can outspeed Sigilyph, which is very likely if its nature boosts Speed; one Swords Dance allows it to OHKO with Shadow Claw, but Sigilyph knows and can use Reflect, and if it does outspeed, its Psychic will almost two-shot Lucario before it goes down. Additionally, one Swords Dance is not enough to also OHKO Slowking; Shadow Claw has a chance, but not a certainty, to do so, though Lucario can take a Psychic from it even after taking one from Sigilyph. Meowstic is less likely than Slowking to be OHKOed, as well, and being the fastest of Olympia's Pokémon, it's also the most likely to outspeed Lucario. Another option is to use Swords Dance twice against Sigilyph, instead of just once; without Reflect up, OHKOs will be scored all across the board. Otherwise, Mega Lucario can OHKO all of Olympia's team with Shadow Claw, after a single Swords Dance (and assuming Reflect is down).
Lysandre battle #1 (Lysandre Labs): Lucario's Close Combat OHKOs Mienfoo, Murkrow and Pyroar, but Pyroar is very likely to outspeed any Lucario, and may also outspeed ones with a Speed-boosting nature; a minimum Speed of 131 is required to guarantee that Lucario will go first, else Pyroar will OHKO it with Fire Blast, regardless of Special Defense drops. Mega Lucario has higher base Speed than Pyroar, and can therefore face it without fear. Gyarados knows Earthquake, and must be avoided even by Mega Lucario.
Aliana (Lysandre Labs): Lucario should use Swords Dance against Mightyena, or 2HKO it with Power-Up Punch; at +2 in Attack, its Close Combat OHKOs Druddigon as well, without a need for Mega Evolution.
Celosia (Lysandre Labs): A regular Lucario can use Swords Dance against Manectric, then OHKO it with Close Combat; Drapion is highly likely to be OHKOed by the same move after a Swords Dance, and even if not, Lucario can take any of Drapion's moves even at -2 Defense due to resisting them all twice or being immune to them. Lucario can also live a Flamethrower from Manectric, but not two, so it needs to outspeed in order to win; a Lucario with a Speed-boosting nature is likely to do so, but only Mega Lucario has the guarantee.
Bryony (Lysandre Labs): Close Combat, Close Combat, GG.
Mable (Lysandre Labs): Lucario OHKOs both Houndoom and Weavile with Close Combat, but needs to outspeed Houndoom to stay safe, as its Flamethrower is a fairly likely OHKO. Only Speed-lowering natures will realistically have a problem outspeeding, however, and even though Lucario will be outsped by Weavile, its Low Sweep is only a 2HKO. A Lucario with a nature detrimental to Speed can still win by going Mega.
Xerosic (Lysandre Labs): Crobat outspeeds Lucario, but the most it can do is a 4HKO with Air Slash, which Lucario can beat by 2HKOing with Rock Tomb after a Swords Dance. The +2 Attack boost will also allow it to OHKO Malamar with Close Combat, which would otherwise beat Lucario with Superpower, an OHKO after Lucario's Defense drop. A Lucario with an Attack-lowering nature should use two Swords Dances instead, to secure the OHKO.
Lysandre battle #2 (Team Flare Secret HQ): Lucario must avoid Mienshao, which can outspeed and OHKO with High Jump Kick; only Mega Lucario can OHKO it with Close Combat. Honchkrow can be used to put up a Swords Dance before OHKOing with Close Combat, even as regular Lucario (Mega Lucario OHKOs directly); Pyroar is OHKOed again, providing Lucario can outspeed, which is likely if it has a Speed-boosting nature but hard otherwise, unless Lucario once again goes Mega. Gyarados must be avoided by both, it knows Earthquake.
Xerneas (Team Flare Secret HQ, X only): Lucario cannot win this fight without its Mega Stone. By going Mega, instead, it can 2HKO Xerneas with Metal Claw.
Yveltal (Team Flare Secret HQ, Y only): A regular Lucario cannot win against Yveltal, though a Mega Lucario can do so by 2HKOing with Close Combat, as Oblivion Wing will not kill even after a Special Defense drop. Swords Dance will allow it to survive even a critical hit, if it comes to be.
Lysandre battle #3 (Team Flare Secret HQ): Lucario will get killed by Mienshao's High Jump Kick if it puts up a fight, but Mega Lucario can OHKO it with Close Combat instead. Honchkrow is not OHKOed, but can be after a Swords Dance as regular Lucario; Mega Lucario can simply OHKO. Pyroar can be OHKOed by both Lucario and Mega Lucario, but only the latter or a regular Lucario with a Speed-boosting nature will outspeed and not get killed by Fire Blast. The now-Mega Gyarados is OHKOed by Close Combat as regular Lucario if a prior Swords Dance setup is still present; else, Mega Gyarados will kill with Earthquake. Mega Lucario does not need a Swords Dance to OHKO with Close Combat.
Professor Sycamore (Couriway Town): The lead Venusaur can be used to set up two Swords Dances to then OHKO with Return, the move with the highest power that Lucario can use to dispose of Venusaur; Petal Dance takes at least three turns to KO, so Lucario will win. At +4 Attack, Return will also OHKO Charizard, which would otherwise possibly kill Lucario with Flamethrower in the event Rock Slide missed; Blastoise is OHKOed by Close Combat instead. Lucario needs to outspeed Charizard, which it usually will, but Speed-lowering natures are unlikely to accomplish this without Mega Evolving. Mega Lucario still needs two Swords Dances to OHKO Venusaur, so the matchup is the same.
Shauna (Route 19): Delcatty is perfect setup material for Lucario, which can solo Shauna's team with Swords Dance and Close Combat. If Shauna's starter is Chesnaught, Lucario will need the +4 in Attack to OHKO it, whereas Greninja and Delphox are OHKOed at +2, Delphox with Shadow Claw rather than Close Combat. Lucario's Speed is lower than Delphox's, so it needs a Speed-boosting nature or a number of Speed EVs to win; Speed-lowering natures may only win by Mega Evolving. For Mega Lucario, one Swords Dance is sufficient to OHKO Chesnaught, as well.
Tierno (Route 19): Lucario can dispose of Talonflame with Rock Slide, and even if it misses once, it can take two Acrobatics (or one after a Swords Dance). It can also OHKO Roserade with Return after a Swords Dance, and Crawdaunt is OHKOed by Close Combat regardless of stat boosts. Mega Lucario has the same matchup.
Trevor (Route 19): Raichu is OHKOed by Close Combat, and Aerodactyl is also OHKOed by it after a Swords Dance. The +2 Attack serves Lucario well to also OHKO Florges with Poison Jab or Metal Claw. Going Mega is not necessary, unless Lucario's moveset is different; for example, if Lucario has Return instead of Poison or Steel coverage, then only Mega Lucario is capable of OHKOing Florges after a single Swords Dance. Lucario should also not attempt to fight Aerodactyl if its health is low, due to Supersonic causing massive self-inflicted damage when Lucario's Attack is boosted.
Gym #8 - Wulfric (Snowbelle City, Ice-type): Lucario OHKOs Abomasnow and Cryogonal with Close Combat and Avalugg with Aura Sphere, no setups necessary. It is better for Lucario to not boost its Attack in this fight, since Cryogonal may outspeed it - unless Lucario's nature favours Speed - and use Confuse Ray. Mega Lucario does not have this issue.
Rival (Victory Road): Meowstic is 2HKOed by Shadow Claw, so Lucario can use the first turn to Swords Dance instead. If the rival's starter is Chesnaught, the battle is easy: after KOing Meowstic, Lucario's Attack will be at +2, and allow it to OHKO Vaporeon; an additional Swords Dance should be used against Altaria, to secure the Close Combat OHKO against Chesnaught as well. At +4, Altaria is highly likely to be OHKOed by Return, and Moonblast only 3HKOs at -1 Special Defense either way. If Chesnaught comes out right after Meowstic, Lucario needs to switch, as its Brick Break is close to an OHKO. An alternative for this specific team is to run a Calm Mind set: Absol is OHKOed by Aura Sphere, Meowstic by Shadow Ball starting at +2, Vaporeon is 2HKOed by Aura Sphere from +2 onwards and so is Altaria by Dragon Pulse, while Chesnaught is OHKOed by Psychic at +2 or higher. This set, however, leaves out one of the Pokémon since it requires four attacking moves as well as Calm Mind. If the rival's starter is Greninja instead, the Swords Dance alternative works; Meowstic, Absol and Altaria are treated as stated, Flareon is OHKOed by Close Combat (or even Return, to avoid additional defensive drops), and Greninja is also OHKOed. Lucario can live a five-hit Water Shuriken without critical hits if its Defense is at -2 or better. If the rival's starter is Delphox, Lucario must run Calm Mind and use it three times to OHKO Meowstic and Delphox with Shadow Ball, Altaria with Dragon Pulse, and Absol and Jolteon with Aura Sphere; it also will need healing during the fight, because Meowstic's Psychic and Delphox's Flamethrower piled up would otherwise end it. Mega Lucario can use Swords Dance twice against either team, then OHKO with Close Combat (Absol, Vaporeon, Chesnaught, Greninja), Earthquake (Jolteon, Flareon, Delphox), or Shadow Claw (Meowstic), while Altaria remains a 2HKO, but its moves are not that strong. Even Mega Lucario needs to be wary of Greninja in low health, as its Water Shuriken has priority.
Elite Four Wikstrom (Pokémon League, Ironworks Chamber, Steel-type): Lucario can take up to two Dazzling Gleams from Klefki, so unless Klefki uses Torment, it can use Swords Dance twice before OHKOing it with Close Combat. Probopass is OHKOed by Bone Rush even with just two hits, if Lucario's Attack is at +2 or higher; its Earth Power will only 2-3HKO, so even one Bone Rush miss is not a problem. Bone Rush is needed, since Probopass' ability is Sturdy. Scizor is also OHKOed after one Swords Dance, but Aegislash-Shield will be OHKOed only by Earthquake after Lucario hits +4 and would otherwise one-shot Lucario with Sacred Sword (as Aegislash-Blade) after a single Defense drop. Mega Lucario only needs one Swords Dance to score the same OHKOs.
Elite Four Malva (Pokémon League, Blazing Chamber, Fire-type): Since Pyroar's ability is Rivalry, it will not OHKO a male Lucario with Flamethrower, though it may still outspeed if Lucario's nature does not boost Speed and/or Lucario is lacking EVs in the stat. Only Close Combat OHKOs, however; Earthquake is not sufficient. Torkoal only 2HKOs with Earthquake as well, and can be used to Swords Dance once; after a setup, Earthquake OHKOs both Torkoal and Chandelure, though it will only OHKO the former if the Expert Belt is being held. Talonflame must be avoided, as it would otherwise outspeed and kill Lucario with Flare Blitz. Mega Lucario has the same matchup, though it can also take on Talonflame with Rock Tomb or Rock Slide if its nature boosts Speed; if the move fails, Mega Lucario can take a Flare Blitz from Talonflame, but not two. Hasty ones still might be OHKOed by it, if the damage roll is high.
Elite Four Drasna (Pokémon League, Dragonmark Chamber, Dragon-type): Lucario can use Swords Dance twice against Dragalge, which can at best 4HKO; after that, Return OHKOs all of Drasna's Pokémon. Specially based Lucario can use Calm Mind twice, instead, and then OHKO everything with Dragon Pulse. Mega Lucario's matchup is the exact same.
Elite Four Siebold (Pokémon League, Flood Chamber, Water-type): Lucario can OHKO Clawitzer after a Swords Dance with its Close Combat, but Clawitzer's Mega Launcher-boosted Aura Sphere comes dangerously close to OHKOing, and the setup would be moot against Gyarados either way, which makes even Mega Lucario run away in fear of the Dragon Dance and Earthquake combination. Mega Lucario does, however, OHKO Clawitzer with Close Combat without any setups. Lucario is disadvantaged against Starmie, as it cannot fight it with any prior setups due to Gyarados' likely entrance on the battlefield, and its Surf 3HKOs; Mega Lucario can 2HKO Starmie with Shadow Claw instead, or even Close Combat. Both regular Lucario and Mega Lucario OHKO Barbaracle with Close Combat.
Champion Diantha (Pokémon League, Radiant Chamber): A regular Lucario gets beaten by Hawlucha's Flying Press, which 2HKOs, as Lucario will never be faster than Hawlucha; Mega Lucario, instead, can use Swords Dance against it and then OHKO with Close Combat. Lucario's best STAB also OHKOs Tyrantrum and Aurorus, no matter whether Lucario has Mega Evolved or not (regular Lucario needs the Expert Belt to OHKO Tyrantrum); Metal Claw can OHKO Aurorus even as regular Lucario, too, saving a defensive drop but also introducing a 5% miss chance. Gourgeist can be 2HKOed with Shadow Ball even if Lucario is running an otherwise physical set, because its Special Defense is much lower than its Defense; Trick-or-Treat may, however, be a problem if Lucario's health is low, since its Shadow Sneak will then strike for twice as much damage. Mega Lucario may do better with Shadow Claw, which 2HKOs after a Swords Dance, since Mega Lucario is capable of defeating all of Diantha's Pokémon that come before Gourgeist, unlike regular Lucario. The latter also has issues fighting Goodra, which 2HKOs with Fire Blast, as it is highly unlikely for Lucario to find room to set up without Mega Evolving; Mega Lucario OHKOs Goodra with Close Combat even without any setups. Regular Lucario can, however, 2HKO Mega Gardevoir with Metal Claw or Poison Jab if it outspeeds, since it can live a Moonblast unless it crits; Mega Lucario scores a net OHKO, but only with Metal Claw.
Post-Game: Everything happens for a reason, including Smogon bans. Mega Lucario can go ahead and get 'em.
Riolu's initial moveset consists of Foresight, Quick Attack, Endure and Counter. It then gets another priority move at level 11, in the form of Feint. While far from stellar or ideal to start off, it does also learn Force Palm at level 15, which is plentiful STAB for a while longer in the game; this is also the last move worth learning before the evolution into Lucario. Evolving Riolu at level 15 is ideal: it will allow it to learn Power-Up Punch at the very same level as Lucario, which is close to broken at this point in the game. At level 19, Riolu gets Copycat, which is useless, whereas Lucario gets the much more helpful Swords Dance; as its bulk is high for this point in the game. Swords Dance is also a move worth keeping in the long run, and will later gain the benefit of flexibility as it can also be taught to Lucario via TM. Keep in mind, however, that Lucario's Speed is good, but not very high; it will be outsped by some Pokémon later during the adventure, and against them, setting up may not be the best option. At level 24, Riolu learns Screech, which is in every possible way worse than Swords Dance, and Lucario learns Metal Sound, which might be situationally useful but will generally not be worth the moveslot. Level 29 sports Reversal for Riolu, which can work with Endure but is not exactly ideal with Lucario's only better-than-average Speed, and the much more notable Bone Rush for Lucario. However, at this point in the game, the Dig TM should be already available, and the move provides a better and more reliable damage output than Bone Rush, as well as having better accuracy; however, Bone Rush is essential against Clemont's Magneton, particularly if Lucario is not going to be Mega Evolved during the gym battle. Riolu doesn't learn any other moves besides Nasty Plot at 47 and Final Gambit at 50, neither of which it will want, the former because Riolu will never survive as Riolu for that long, and the latter for obvious reasons. Lucario, instead, learns Quick Guard at 33 and then Me First at 37, neither of which is very notable, but it also gets its ex-signature move Aura Sphere at 42, which is nothing short of fantastic: flawless accuracy, high base power, and Adaptability to support the damage, if Lucario goes Mega. Calm Mind, at 47, will support special sets very well, possibly even more so than Riolu's way too late Nasty Plot, as Lucario's special bulk also needs to be boosted to survive a few hits; the useless Heal Pulse at 51 will obviously be ignored in favour of level 55's Close Combat, the most amazing move Lucario gets access to. Close Combat OHKOs everything that's weak to it in Mega form, and a lot of Pokémon that are not weak to it too, and it will also deal incredibly high amounts of damage to those that resist it. The last two moves, Dragon Pulse and ExtremeSpeed, which come respectively at level 60 and 65, may be useful in some sets but not others, depending on Lucario's nature and stats; Lucario can take them or leave them, depending on the immediate necessities of the team. It should also be noted that Dragon Pulse, Close Combat and Aura Sphere are all moves that Lucario learns at level 1 as well, and as such they are accessible as soon as Dendemille Town, through the Move Reminder. Another move worth of mention that the Move Reminder offers is Metal Claw, which is the only Steel STAB Lucario can learn before the postgame.
The TM pool for Lucario is vaster than most Pokémon's, and there are so many options to pick from, for each set.
For physically-oriented ones, Bulk Up and Swords Dance (which is also a level-up move) are both very good for setup purposes; if you received your Lucario from Korrina, Bulk Up might work better, as its Hasty nature leaves a visible dent in its Defense. Power-Up Punch is another viable option for the same purpose, although it trades away the Defense boost for damage. Return is available early in the game, and will obviously work great on an already evolved Lucario, though of course Normal coverage is not so useful later in the game; Dig, instead, does its job very well against Electric- and Poison-types, the latter of which Lucario is a great counter for. Earthquake is obviously better than Dig, though available much later. Rock Slide and Stone Edge both provide Rock-solid options against many other types as well, though their accuracy leaves something to be desired; if needed, Lucario can opt for Hone Claws over the aforementioned setup moves, as a single usage of the move boosts the accuracy of its available Rock coverage to beyond 100%. Both Shadow Claw and Poison Jab are very good for additional coverage; the former hits Ghost- and Psychic-types, and the latter gives Lucario a super effective option against Fairy-types before Dendemille Town, where Metal Claw becomes available. It should also be noted that, if Lucario does not Mega Evolve, Poison Jab has almost as much base power as Metal Claw, and slightly better accuracy. Low Sweep also deserves a mention for being an early game Fighting move, which Lucario will need even more than Riolu if it evolved before learning Force Palm.
Special sets will, of course, benefit greatly from Calm Mind, which should be the go-to setup move. Both Dark Pulse and Shadow Ball are excellent complements for Aura Sphere, and achieve near-perfect coverage when combined with it; there is very little that can resist both. Psychic also works for general coverage purposes, if the team needs a counter for Fighting-types, though Lucario should hopefully never have to fight any of them due to having a Fighting weakness itself. Lastly, Hidden Power might be worth considering for coverage, depending on its type; a Steel-type Hidden Power would actually do great for Lucario, as its only special Steel move - Flash Cannon, available by TM - is a postgame exclusive.
Physical: Bulk Up / Swords Dance, Close Combat, Metal Claw, Earthquake / Shadow Claw / Rock Slide
Special: Calm Mind, Aura Sphere, Dragon Pulse, Shadow Ball / Dark Pulse / Hidden Power [Steel]
Water-types: Nothing covers Lucario's Fire and Ground weaknesses better and more easily than the common, near-omnipresent Water-types do. Lucario's Grass resistance also returns them the favour, and its decent Ground movepool will also allow it to somewhat cover for their Electric weakness, if needed. A Water-type should almost always be present on a team.
Psychic- or Fairy-types: Fighting-types are best covered by a type that resists them and can deal super effective damage; Psychic and Fairy fit this description, and therefore have good synergy with Lucario, whose STABs are good against their respective weaknesses.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Riolu Line Ratings
What Nature do I want? The gift Lucario from the Tower of Mastery is always Hasty, which is an okay nature. If Riolu was caught in the wild, instead, any nature that boosts either offensive stat and lowers any defensive stat works very well, with a preference for Attack; the best options are Lonely and Naughty, with Mild and Rash being runner-ups.
What Ability do I want? Neither makes a significant difference, unless Lucario is really slow. Inner Focus, however, can be useful to prevent Fake Out flinching, and getting rid of enemies faster; still, Steadfast is not that much worse, and after Lucario can Mega Evolve it will not matter either way, as the Mega version always has Adaptability.
At what point in the game should I be evolved? Whenever possible, since the player has full control over friendship evolutions; however, Riolu should be kept unevolved at least until level 15, when it learns Force Palm. Level 15 is actually ideal for evolution, as Lucario will also learn Power-Up Punch at that level; evolving Lucario so early is not exceedingly difficult, either, as it only requires some more walking on top of its training routine. Having a Lucario before Grant will also provide a fantastic counter for the second gym. Make sure to evolve Lucario no later than before the third gym fight, however, as Riolu tends to fall heavily short in bulk and power around then.
How good is the Riolu line in a Nuzlocke? Amazing in every possible way. It has a movepool like no other in both physical and special terms, and its early Mega Evolution capability makes it excellent for tackling almost any opponent, no matter how things turn out.