To defeat bastion, I'm pretty sure you have to be Wolverine, and since
Wolverine is my best character, here are some pretty helpful moves:
    Animal Instinct, level 1, back and AB at the same time, does a
barrage of punches and cuts
    Precise cut, level 2, AB at the same time, slices the opponent 20
times into the air
    This next move I don't know what it is called, but you jump up into
the air and press AB at the same time, its level 2, and it is some
spiral cut attack
    Berserker Fury, level 3, forward and AB at the same time, advanced
version of Animal Instinct.
    Regeneration, level 4, XY at the same time, regenerates about half
of your health.