Alright I'll focus on fixing the movement first, and then I'll do shading. Here's what I got. I fixed the torso and legs so that they don't stretch, and I delayed the animation of the right arm. I didn't really make him shift his weight from one leg to the other, because it's only a six frame animation, and I don't think that's enough space to do it effectively. Tips? I think the legs look a bit weird, but I'm not sure how to fix them.
EDIT:
After looking at this for a little while I realized that the head should move more, since the Demogorgon is supposed to have a long neck, so here is a modified version where his head bobs a little more to the side. Let me know what you think about this.