Nice job, nice shading etc.
There aren't really any problems, considering it's still a WIP... I suggest giving the eyes... or what ever that's called, more of a glow. It would give a more menacing look. I can't really tell ATM, but the legs seem a bit short, maybe because the back leg appears to be a lot shorter then the other. If it's due to distance, then I suggest making the other arm to the back more as well. Are the abs and parts of the arm suppose to be skin? If so, I would suggest adding just a tad more contrast to the armor.
Also, is this for wonderbros? Because I'm a fan of the game, and would like to seem some progress for it. I noticed you posted a bit more stuff for it on pixeljoint. Anyway, I tried getting the style. You can look through my posts if you'd like to see it. I pm'd you on pixeljoint, btw.
Good luck, I suppose.