Alright Asuma, let's try to move in for the kill. You've done great so far.

Move in with a Faint attack to knock Grand-Sama of balance, then while he's staggering use a Dynamic punch. Finish with Crush Claw. If for some reason the combo won't work, use brick break on your second action

Faint Attack+Dynamic Punch/~Brick Break~Crush Claw