I really like where you are heading with this. The posture is really good, also the proportions work well (if you intend to make this a kinda bulky, brute guy)
However, I'd think about adding some white for the eye. Without the helmet the "blackness" works well, however with the helmet on your loosing a little bit too much of the facial features for my taste - I'd try to clean up the facial area a bit to make it more readable. Is that a mustache?
The right leg looks a bit weird. I think you are trying to have him look aggressive even in the standing stance, which works nicely, but I think if you could pull the right foot a bit to the right you could make him look much more "stable".
And I agree, while I like the Helmet I'd try how it looks like with one of these typical centurion mohawks on top