Lucario is frail is crap. Meaning there are only two EV spreads you should really consider running on him.
252 SP ATK / 252 SPEED / 4 HP ( Special sweeper )
OR
252 ATK / 252 SPEED / 4 HP ( Physical sweeper )
Now here are some Lucario sets that you probably can't get unless you're hatching that Riolu on a 4th gen game.
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Lucario#Life Orb
Ability: Variable ( Variable basically means it doesn't really matter )
Nature: Jolly
EVs: 252 ATK / 252 SPEED / 4 HP
Extreme Speed ( Priority )
Close Combat ( Hits hard. He's too frail to take a hit anyway )
Earthquake ( Good coverage )
Ice Punch ( More good coverage. Especially flying types )
That's my preferred Lucario.
Other sets....
Lucario#Choice Scarf
Ability: Variable
Nature: Modest
EVs: 252 SP ATK / 252 SPEED / 4 HP
Aura Sphere ( Power + Accuracy + STAB )
Dark Pulse ( Gives some great coverage with fighting )
Dragon Pulse ( Eh.. filler )
Flash Cannon ( STAB..? Filler )
Basically a special scarf set. Fun stuff to use.
And lastly.
Lucario@Air Balloon
Ability: Variable
Nature: Jolly
EVs: 252 ATK / 252 SPEED / 4 HP
Hone Claws ( Hope that you get a really good switch to set this up on.. )
Hi Jump Kick ( Fun fun fun... STAB )
Rock Slide ( Coverage )
Blaze Kick ( Coverage )
Also, if you try to go for a mixed set ( I'm not gonna post one, sorry. )
Then you would want this EV spread.
196 ATK / 60 SP ATK / 252 SPEED
Putting more into Attack because he has naturally higher special attack.
