KK hu fold river on straity board?

I would most likely bet/fold river for thin value, but that's villain depended with a 20bb bet.
I expect villains are most of the time passive. Now you only a weaker 2 pair and I don't think villain would play those hands and is folding most likely better.

Cheers,
SDK1987

From his initial calling range what are you still beating on the river that called 2 decent sized bets? Without readings on the villian except he's a rec (not full stacked) this is a hard call and I would also prefer much a blockbet/fold. =>SDK1987 is 100% right, they are passive so any re-raise is a good tell to fold, while you get value/calls from hands you have beat.
His sizing on river is usually value heavy from my experience (it's designed so you call any AQ or AJ or overpairs).

What has you beat: Any 9x, Tx, 88, TT (JJ, QQ should have 3b pre)
You are beating: QJ & 78s (AQ, AJ should have 3b pre)
If he had lower pair or only hit the 8 he would probably check river thinking of showdown value.
Sick runout but I would assume I'm beat as played.

I agree with SDK I think at most you want to bet here is 1/3 - 1/4 pot. It's thin and he might fold his J/Qx here anyway. I'd imagine betting 30% or checking here is fine.
You also block KJ KQ which is what we'd be betting for on the river. Villain has all 9x 10x here. Probably leaning on a x/f on the river here.