That's a trait common to the weasel family. Our ferret Mindy, all of two pounds at her fighting weight, never hesitated to pick a fight with one of our 10 pound cats or even our 70 pound dog. She brought him to his knees once by clamping onto his lip and not letting go. :-)
What? Oh, the animal. Real wolverines are cool, too.
I remember seeing a film clip (a long time ago) where a wolverine attacked a freakin' bear! Those buggers don't know when to back down! ;)