He should really be stepping forward with his right leg. Upper body movement is good, though rigid
Ok, your animations are epic.
the arm should twist when you punch and you take a step forward. I think you could also add more frames to it.
edit:
also, the arm makes an L on your waist, then it goes up and to the front rotating with your body and a step.
@DawnBringer: To maintain his center of balance. You have to throw your center-of-balance forward (i.e. "put your body into it") to give the punch serious power. The danger is if you don't also slide your foot, you're borderline falling-forward. Much of Judo et al is built around exploiting this - when someone is that far off balance, it takes very little effort to pull them off their feet.
@Faceless: Stepping forward with either leg is equally valid, according to various martial arts. They fight over it, but all participants in the discussion are obviously effective, and are venerable martial arts dating back to "Ye Olden Tymes", so I figure whichever ones vouch for it can't be completely incompetent.