+ Veins look good
Beard texture
- The shading seems a bit random and the hues are really sharp. Gives it that cheap "Gonzossm" feel
His shoulders are really wimpy
The vein on the forehead is too big
The scar design doesn't look deliberate. (make the scar with less jagged angles)
Eyes are too big (if you're looking for a more realistic style)
I'm no critic, but those caught my eye. I don't know about your style of art, but for me (i like cartoony characters) detail: less is more.