The top one looks very strange because his head keeps jumping up and down and his sword appears from nowhere and extends down to his feet. You probably want to think of the perspective and try to make it look like it's expanding towards the viewer and not into the ground.
But in general, try to get more extreme movements, since those are rather subtle, except for the head bobbing in the top one.
I think you got the right ideas of how the body twists and that you lean forward to stab. But you need to change the perspectives and shading more.
The bobbing head would look better if the body got a lot shorter and compressed and the top of the head would become visible.
Also don't forget to add a shadow over the body since he's leaning forward.