The sketch is generally good.. the coat looks mighty well done, and his muscles and arms look quite neat as well, but it looks (to me at least) that you 'messed' up a rather critical section... his butt and thighs. Maybe it's the fact that that area is all done in black? In any case, his thighs don't seem well shaped enough, and the way they connect to his torso seems 'wrong' too (the legs connect too close, it seems). As for the butt, I'd say it could either be the angle (not so likely now that I think about it), or it's the way the legs connect to it (which I think would be the case)... anyway, if it weren't for that minor section, I would have said this sketch is really well done.

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