50NL Full House, River Action

[Maunzekater]

Very, very unlikely villain has AA/KK here. He had the chance to raise preflop when everybody checked to him and he didn't do it, not even a donktastic pot-sweetening minraise.
His calling range is huge, we all know that and i will not make big speculations. He might even limp with AKs, because he didn't hit the flop the last 3 times and had to fold to a bet.

Flop:
everybody checks around, seems like no additional information. But his check makes it even less likely CO has AA/KK. If he slowplayed preflop then this would be the time to wake up. He is last to act, why the hell should he give freecards on this board?

Same for the turn. The board becomes very nasty for any slowplayed set, even a habitual slowplayer has to raise here. Not only to fold out draws but to make the pot bigger.
Slowplaying really doesn't make any sense anymore if he has AA/KK/JJ.