I have KK, what about him????

[McGahee]

Ignoring the river action, I would check/call the river. Lots of players will (stupidly) play a weak Ace like this. So he's going to call a bet every time and also bet when you check to him, but you might induce a bluff from a busted spade draw when you check.
As you played it the river is a very easy fold.