I was experimenting with portraits on my brother, and this was my favorite. The left half of his face seems darker, but I was pleased, nonetheless, with the fact that his eyes were still visible. Would a flash have been helpful? (i don't have one-- or know anything about them, for that matter).
Actually, I think the darkness(which still shows detail) on the left side adds some form and shape to his face. You've also got some sparkle in his eyes, so, although fill-flash is a very useful tool, I don't think it's needed here. A nit-pick would be his right arm...besides his hand being chopped off, it just appears to be at an awkward angle. Your background is nicely blurred, so overall, very well done!
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