The problem is the overall sprite, nothing is right, I'm afraid to say. There are much more experienced artists who would point out the problems, but as a novice, I coudl try.
First of all, the head, it's almost too much triangle like, it should be more eggy/oval like, his hair starts at an odd place and human ears should never be in that position. The way his head faces nearly contradicts his body angle. For the animation, it looks odd how everything but the arms and head don't move, if you want to make him more real, you should move more parts of him, even the slightest pixels will do the job.
Now to the anatomy and perspective, his torso anatomy is off, his chest muscles shouldn't go up like that and end that far, in my knowledge, and his six-pack that's visible shouldn't bend like that, it looks like it's coming from top right to bottom left. His arms, additionally, don't look very good, you should study how the arm and hand looks at such an angle, picture yourself in the pose and breathing in much the same way as he does. Second, you should reduce or refine the muscles on his legs, and finally, you should redo the shading and get rid of the. . Almost odd looking circular shapes near his groin. You know that looks like an insane weakpoint.
