Hey souly, it's looking pretty good. I especially like the jump and transformation animations.
The atatck (?) animation is a bit jerky, and lacks force. Maybe he should wind up first? Like, pull his head back then whip it forwards (strecthing a bit, as he
is on a spring). Or something.. I dunno

The straight gray and red palette struck me as a bit bland, too. I did a small edit (which I hope you don't mind):

Just some shifting in the values. maybe not what you're going for, but it's just a thought. Also, I added some 'depth' to the box, just to spice it up a bit.
These are really looking cool, like I said. Is this set to be an actual game, or just a mockup project?