This looks pretty fantastic, to be honest. It was immediately apparent that he was walking towards someone ready to knock their lights out. As for the punching arm, maybe it's a bit too high. If you trace from his elbow towards the shoulder it seems like his arm either curves in too much or his shoulder is dislocated. It might just be that his shoulder needs a little more presence under his shirt, but I'm not sure to be honest.

Ooh, yeah, I see what you mean. I'm thinking of messing around with another arm position. Maybe instead of pointing downward I can have it raised a bit.

I dunno. Another arm position might be easier to draw, but the way it is now is just so... classic, in that old cartoon kind of way.