Lucario's Counter Picks

B-reversing and wavebouncing are vital techniques to master in order to take full advantage of Lucario's unique air movement options.

Lucario's Down-B is more useful against projectiles and disjointed attacks. It's damage depends on Lucario's %. If used offstage, always make the attack go towards the stage.

Characters that KO Lucario early are always at an advantage. The other issues he has to contend with is his short attack range, and his poor Out of Shield options.

Characters than can kill early or have easy kill confirms are bad matchups and vice versa.

It seems that lucario’s hurtbox priority is lower than most top-tier characters, so baiting rather than trying to trade is essential (along with the technique comment already posted here)