Megatherium

While exploring the Amazon, Xavier Mykenos stumbled upon a hidden tribe of native Amazonians. These Amazons had tamed one of the most impressive beasts of old, the Giant Ground Sloth. Thought to be extinct, Xavier took the opportunity to further science by living with the tribe and learning their ways. Eventually they allowed him to become a full-fledged member of their group, teaching him their mystic means of empathic sloth control. Now whenever he needs to, Xavier can call upon the spirits of the behemoth, transforming him into the lumbering titan known as MEGATHERIUM.

The powerhouse of the squad. He’s slow, but tough. And look at those claws! Kind of a Sasquatch + Wolverine cranked all the way up to eleven. Osteoderms (aka bits of bone) under the skin made him as durable as bane, and believe it or not, he can float! While he can’t match Mantis Shrimp or Titanis for speed, he can take punishment while dishing it out. Surprisingly, Xavier is also a master of camouflage, as he emits no odor, can move through dense forest silently, and can remain hiding from view for millennia (theoretically, at least).

From: http://ifanboy.com/articles/columns/obscure-animal-superheroes-i-want-to-see/