This is quite masterful! I'm not entirely sure what to tell you. Your use of angled, straight lines for the shading shows great mastery, patience and understanding of art techniques and just the subject in general.

I'm not really sure if there is anything negative that I can say for this, his facial expression and body language is powerful and quite fascinating. The only piece of advise that I can think to offer is perhaps you could have put a little more shading on the hand, but beyond that I am impressed.

The clothing also looks like it took quite a lot of effort and time, I really hope you keep up the good work.