V has VPIP 34% and 3bet 4% over 300 hands.

With his extremely low 3bet and high VPIP I think AQ, A5, and 55 are all in his range.
The flop and turn I think are easy calls since he can have flush draws with the A of spades.
On this river I still beat missed flush draws, but I'm not sure he bets with the A of spades. So really the only missed flushes I beat are KJ and JT and a few other suited connectors. Is folding this river too nitty?

Yatahay Network - $0.10 NL FAST (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4: http://www.pokertracker.com

BTN: 120 BB
SB: 68.3 BB
BB: 120 BB
UTG: 207.6 BB
MP: 100 BB
Hero (CO): 809.1 BB

SB posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has Ad Kc
fold, fold, Hero raises to 2.5 BB, BTN calls 2.5 BB, fold, fold

Flop : (6.5 BB, 2 players) Qs Ac 5s
Hero bets 4 BB, BTN raises to 14.8 BB, Hero calls 10.8 BB

Turn : (36.1 BB, 2 players) Jc
Hero checks, BTN bets 27 BB, Hero calls 27 BB

River : (90.1 BB, 2 players) 8h
Hero checks, BTN bets 75.7 BB and is all-in, fold

I think it is unlikely for a loose-passive to be turning a pair into a bluff on the river. I also think it is unlikely for him to raise the flop and bet the turn with just top pair + flush draw. I would definitely fold the river. I also feel like a turn fold is probably best against this opponent.

I like the idea of folding turn. I couldn't do it.

how often do you typically face aggression on Axx boards that you have cbet as pre flop aggressor. we're never folding flop but i think a exploit fold somewhere isnt ridiculous. unlucky.

I like a bigger bet on the flop.

If this guy is enough of a lunatic to bluff you on this board, good luck to him. I'm okay with folding turn when we can defend with better and we're only happy on a couple of river cards.

I would bet smaller on flop - typically I cbet 33% - 50% pot
I also X flops like this to X/call at some frequency to protect my X range as our hand is medium strength and BN calling range is similar to our RFI range but capped
I'm folding turn