Well, I'm no animation buff, but see if this helps you out.
That jitter on his right leg is pretty distracting, so you might want to remove that.
I think you might be onto something with the other leg, though you should probably manipulate the upper leg more when he lowers, since that's the part that actually bends.
At the lowest part of the bend, you can put some pixels around the upper leg of his right leg since that part is more foreshortened, then make it transition back to the highest part.
You should probably make the fists bounce together, where they are highest at the highest point of the animation, and transition to the lowest.
Not sure if that makes any sense, but hopefully it helps somehow!
EDIT: Oh, I forgot to mention, maybe you can study some fighting game stances to learn some of animation trends. You know, take frame by frame, and observe how parts change position, and take note of the timing.
That jitter on his right leg is pretty distracting, so you might want to remove that.
I think you might be onto something with the other leg, though you should probably manipulate the upper leg more when he lowers, since that's the part that actually bends.
At the lowest part of the bend, you can put some pixels around the upper leg of his right leg since that part is more foreshortened, then make it transition back to the highest part.
You should probably make the fists bounce together, where they are highest at the highest point of the animation, and transition to the lowest.
Not sure if that makes any sense, but hopefully it helps somehow!
EDIT: Oh, I forgot to mention, maybe you can study some fighting game stances to learn some of animation trends. You know, take frame by frame, and observe how parts change position, and take note of the timing.