Villian is very actief
How to play this?

PokerStars, $50 + $5 - Hold'em No Limit - 300/600 (75 ante) - 8 players
Hand delivered by Pokeit

Lorika_Ch (UTG): 93,352 (156 bb)
krabinalouco (UTG+1): 29,704 (50 bb)
sundricus87 (MP): 57,672 (96 bb)
quimmixxx (MP+1): 60,683 (101 bb)
_nikita555123 (CO): 49,040 (82 bb)
bookerApoker (BU): 139,756 (233 bb)
mixjuice (SB): 71,853 (120 bb)
kimos (BB): 48,650 (81 bb)

Pre-Flop: (1,500) Hero (kimos) is BB with K 6
Lorika_Ch (UTG) raises to 1,200, 1 fold, sundricus87 (MP) calls 1,200, 4 players fold, kimos (BB) calls 600

Flop: (4,500) 3 5 3 (3 players)
kimos (BB) checks, Lorika_Ch (UTG) checks, sundricus87 (MP) bets 4,500, kimos (BB) calls 4,500, Lorika_Ch (UTG) folds

Turn: (13,500) A (2 players)
kimos (BB) bets 4,455, sundricus87 (MP) calls 4,455

River: (22,410) 8 (2 players)
kimos (BB) bets 11,400, sundricus87 (MP) calls 11,400

V is a very active....reg? fish? It kinda matters.

Flop pot stab looks like a protection bet with 5x or 66+.
So, I guess turn lead works in theory...?
I'd just X/X turn, it'll get checked back a ton.

Give up river with a busted fd.
Don't bluff a fish?
I get that you're repping Ax with a half pot river bet but fishy Villain pbb isn't folding anything to a small size when draws miss.

The whole hand just depends on your reads on the 'active' Villain...

Yes, i was indeed repping Ax with Ac.
I agree, i shouldnt have to bluff a fish. he called and won with pair of 4
maybe a larger river bet would had helped

thanks for your answer

Villain opens UTG to an 8 handed table - can easily rule out 5x and it's more bigger pairs/high cards. Turn is not good for you - this is just not a good board in general to be bluffing, especially after he pots the flop. On the river you look like a missed flush draw and now his Ax got there and he's not folding preflop pairs.

Is the turn a semibluff or a blocking bet? He pot cbets and you 1/3 pot donk the turn. Unless he bet pot with air, he is never folding to that bet OTT. It might be OK to discourage another big bet OTT, but it doesn't represent strength, other than you must have something to have called the flop.

I would not bluff the river. All you might get to fold is a worse flush draw, which he is probably less likely to bluff with than if you checked. The turn bet looked really weak, and it is unlikely the offsuit 8 helped you, so you are not representing much.

An ace with a flush draw is a narrow range, and you probably would have checked the turn with it (it is an easy check/call, maybe a checkraise), or at least not led small. Similarly, if you had trips (you have a big nuts advantage OTF, because he should not have trips), it would not make sense at all to play it that way of the flop and turn.

If your determined to rep the ace, c/r turn would be the play or if it goes x/x then re-evaluate on river if you think Gillian is a passive fish then it's going to be hard to get home to fold any pairm

Cbetting pot is not reg style. That play is not that bad, but he is probably a donk/ random/ rec.

Someone who cbets pot is not going to want to fold, regardless of the logic of it. Aside from OPs line representing nothing and no strength, this is an awful situation to bluff.