It looks like a baby form. Pudgy fingers and toes, rounder head, bigger eyes, less muscle definition (not that Mewtwo had much to start with, but he did have the chest plate), and the tail curls on itself at the end. Not to mention that overall, unless proportions are way off, he just simply shrunk.
At first I hated it, then I was like meh, then I looked at it again, and it looks like a Mewtwo with a tail on its head.
Those two sections of other people's comments pretty much explain exactly what I was thinking. That said, 3/10. It's awful, but there's a couple parts of the design I think are okay.