His legs animate a bit wonky, don't you think? Well, more like the transition from the first frame to the last. I imagine there's some way to improve that.
Other than that, I don't really see this as an attack, so much as a parry of sorts. His body language suggests that he's getting out of the way of danger rather than coming at it. One reason is probably due to the initial wind-up looking like a quick poke, and the actual attack looking like he's swiping whatever counter the enemy may have had out of the way. The other reason has to do with him backing and up, and generally being more upright than he should be. My guess is that this guy isn't really an adept fighter, but even so, I think my criticisms still stand. And, if he's meant to be a skilled fighter, even rudimentarily so, then you've got work to do.