This is an amazing artwork. However, this is just my opinion of course (I don't mean to insult or harm you!), I think his nose, mouth, and chin should be more defined, (his jaw squarer, mouth less hard and more curved, nose more close to the mouth if just a little.) Those little, intricate details on his face show proof of how much you worked on it and they look very good! The hair was a little bit forced, but it's nice.
You have some great artwork.