The muscle mass and detail on the top of the body suggest a fit, buff adult man, while the lower waist and legs appear that of an obese old-man. Posture also is odd, hip placement makes it look like he's sitting, while extending a huge closed fist (a weird action).
Stand up. Right now. Do it. Throw a few punches.
Pay attention to how you're balancing your body, how your torso rotates, what your other arm naturally does. Notice the angle your legs are making to your hips.
I suggest using lines that convey a more trim look on the legs and waist, try not to use lines that "sag", meaning they aren't as concave on the lower parts than on the upper one's (of the legs and sides of the torso).