Mewtwo has significant better mobilty, and a projectile that should beat Aura Sphere most of the time unless passing Lucario's 100~120% or so. He gets more range and kill power once damaged, so adjust your playstyle around that. It's easy when Lucario has low %, but becomes increasingly hard when Lucario gets his Aura rage going on. Watch out for Force Palm, try to reflect Aura Spheres with Confusion if you can predict it for easy kills, try to pressure him towards your side of the ledge and bait for a B Throw kill, try and get underneath him from the air and U Air juggle / KO him becuase Lucario cannot really land well... and you should probably be fine.