Proportions: Look all plausible, though if I imagine a fully body, the head might be just a very slight bit too small; the facial features are spot-on in their proportions relative to each other
Expression and character: Very sympathetic!
Hatching: Well done, albeit a bit undecided if it should follow the character's lines, the background, or the shadows -- Could probably improve by hatching in smaller increments. The eyes stick out properly with their finer hatching, giving them really good emphasis.
"Coloring": The character blends into the background in the brighter part of the picture... if that is not wanted, slightly better defined/more connected outlines at the fur fringe could define the distinction better, but that would interact with the way the hatching is perceived
Overall composition: Pictures like this often suffer from having a hard time distinguishing background and character on first look, but this one got that right - maybe it's a question of contrast, so the contrast is good here.
Hm... the line of the arm near the knife blade as well as the hatching right in front of the blade could have used a little more cleanup.
No fur lines on the body? Looks like a sweater. Only recognize that just now -- Maybe a faded kind of graphic on it would help identify it as a piece of clothing on first look.

Overall a good to very good picture, with a very sympathetic character expression. The face probably got the most thought and that paid off.

Thanks for the great feedback! And yes he is wearing a sweater but I didn't make that clear enough. I redrew the face so many times I just wanted to finish so the rest was pretty sloppy :P