You're operating in a bit of a different style than I'm used to, but a few quick things jumped out at me as making him look a little... odd at first glance.

Here's a quick edit and what I changed:

- You are using neither the proportions nor the perspective that he shouldn't have at least some level of visible neck. I only went one pixel higher but it lifts his head from feeling like it sits on his shoulders.
- The shoulders felt way too chunky, even if he's supposed to be a bulky character.
- The legs are the real reason I did the quick edit, I don't think straight legs are perfect, but try standing like your guy is, he's bending his knees sideways. It looks painful.

You're starting in a really good place though, you have great contrast and use colour better than I know I do. Your shoes show a great attention to interesting detail and your light source and shading is consistent across the piece.

This might just be a personal thing, but I'd watch out for the uncanny valley. You've got an interesting mix of styled form with an attempt to throw a bit of realism in there, and I'd recommend pushing a little more one way or another. You can go for further correctness by doing things like putting ears where they should be, rounding out the shoulders more and giving him better posture (I feel like he's hunched forward?) or you can embrace the stylish elements by exaggerating features further. That's all take it or leave it advice though, there's nothing wrong with what you're doing here.