I need your opinion on a hand

[Cactus Cactus]

I am playing 60-120 and there is a huge fish to my left. I don't know too much about how the guy plays but I realize that he is in on every hand. I am UTG with A [img]/images/graemlins/spade.gif[/img] A [img]/images/graemlins/club.gif[/img] I raise andthe fish re-raises me. I re raise, fish re raises, I re raise, fish re raises, I re raise and the fish (after thinking it would be AA vs AA) calls.

The whole table is saying AA vs. KK. Board is 33478. I bet flop, fish calls, I bet turn fish calls. I bet river and the fish says "I know what you have" and then mucks his cards.

What did the fish have?