In your walking animation, the hair is far too bouncy, and in the running animation it has no bounce to it. Also in the walking animation, in frames 4-6 you should take out the dithering on his chest, it's out of place. I think these would look better if you upped the contrast a bit. I like how smooth the walking animation is, but I think in the running you should make his hammer bounce a little. Finally, in your spinning attack you should widen the face. But you're off to a good start, I like what you have here.