I would not go as far as to say it was dramatically underexposed, but it is dark, about a half stop or so. The lighting you used did provide some noticeable modeling which is always good, but there are some things about lighting and texture on the face that are bothersome; they just don't look natural. Too much tweaking in post processing. Also, there is very little separation between model and background. His hair pretty much melts into the background. For this reason, unless you are using a black background you want to to intentionally Zone 2 black, and make other provisions for separation between model and background, you should always light it in some matter. Something else that always bothers me is subjects who are placed directly in the middle of the frame. Although his eyes are aligned iwth the top horizontal third, which is ideal, his face is dead centered. Ideally, at least an eye, or even the bridge of the nose, should be placed at the intersection of the upper horizontal third and one of the vertical thirds. Otherwise, it looks more like a mugshot or passport photo. His shoulders and face are also square to the camera, which makes the composiition more like a mugshot or passport photo. A landscape orientation does not work here; portrait would worked a lot better. Don't be afraid to move the model around and have him animate his poses. What happens outside the frame is sometimes just as important about what happens inside the frame!!!
On the good side though, nice job keeping reflections off his glasses, a lot of people miss that and it's distracting!
