The hair shading is just too random, there's no volume to it. You need to establish volume first, before you try to texture it. The anatomy of the chest/abdomen does not make much sense, I suggest you study some anatomy before continuing. For example, the obliques are non-existant, while the six-pack is ultra defined, right through the clothes (no, there isn't a single bodybuilder buff enough to have his abs show through even the tightest of clothes).
The pants are pretty good, though I'm not sure if you properly established the legs underneath. The drapery of the pants doesn't seem to follow gravity around the knee area. He also doesn't seem to have hips, but I can tell that's part of the original design, so it's probably a matter of gesture. The gesture of the lower torso needs to match up with the hips to create the desired look.
Finally, pose. The manga shot posted above seems to have a very dramatic pose, with tons of tension, reinforcing that the character is bad news. Your pose is very lifeless. The trick here is to put the hips at a different angle from the shoulders. These competing lines will create break points and edges in the anatomy, just like in the manga shot.
