My vote goes to King Kong.
I defy anybody to give me a compelling argument as to a better monkey. Also none of this he's-not-technically-a-monkey business, you know what I mean.
First, my monkey can beat up your monkey. Also he was forcibly taken by boat to America where he finally broke free of his chains before getting shot up by The Man™ so he's like metaphorical and stuff. In conclusion, my monkey can beat up your monkey.