cold called and raised turn. If you think he's a fish then your prob behind. Or are you assuming your ahead??? I don't think he'll fold so if u bet it has to be for value and since i don't think your ahead i'd prob check call since its HU. I think he bets this river with hands your ahead of such as bluffs and weaker kings that he might fold (the bluffs) and raise (the weaker kings + hands that beat you).