Wolverine...
Those little fuckers are one mean son of a bitch. They are smart too. They will track a human for up 50 miles to find your camp and totally trash it when they do. Ran into some of them up in Alaska. About the size of a medium black lab dog and they can run fast enough to take down a caribu, strong enough to kill a bear, have claws about 2 in long, and their skin is so loose that if a predator pins them on the ground they can turn almost completely around inside their own skin.