That is a great attack and I really like the arm and torso motion (although I don't know why you're posting it in someone else's units thread) - but you've got to control the feet better. His left foot shouldn't be sliding backwards like that. It's physically impossible, unless he's got butter on his soles or this is all taking place on an ice rink. A cardinal rule in all animation is that feet stay exactly where they are unless the character is actually taking a step, i.e. lifting the foot off the ground and moving it to another part of the ground.
As I just advised someone else, if you're not sure about how a particular part of the body would move in the animation, try acting it out yourself and see what happens. That applies to feet and legs as well as other parts.