Please settle another argument where I took a lot of heat. I will just explain what happened.

1-2 NL Holdem.

V1, UTG, LAG, not a total maniac. He will fold. But he loves to draw with the wrong odds. He also check raise bluffs a lot. He was caught twice already doing this already. After a couple of rebuys, he won a big pot and has 600 in front.

V2, Mid position, TAG. Very good skilled player. Has about 1000 in front. He is also hero's good friend.

V3, cutoff OMC, very tight weak player. Never raises preflop without aces or kings. I see him call with A-K and A-Q a lot. Only has about 120 in front. He never rebuys until he busts.

Hero is on the button, has 600 in front. Image of being fairly tight but I did catch a bluff earlier.

Hero looks down and sees 4d-5d.

V1 raises to 15. V2 calls. V3 hesitates and calls. I figure I am getting the right odds and the right position to gamble and I call. Blinds fold.

($63)

Flop comes Ad, 6d, 2c.

A pretty good flop for me giving me a gutshot and a flush draw.

V1 surprisingly checks as does V2. V3 bets out 20.00 I am surprised. I am pretty confident V3 either has A-K or A-Q. I decide I have the right odds, even without much implied odds on V3 and I call. V1 calls. V2 Folds.

($123)

The turn is a 3s.

YES! Lady luck has smiled on me tonight. I now have the nuts.

V1 checks, V3 checks (surprised here). It's my move. I really think V1 has nothing. If he had a flush draw he would have shoved after V3 bet and I called. Maybe a weak ace or a small PP. I decide to be a little deceptive. I check.

($123)

River is the Kh. I still have the nuts.

V1 checks and V3 bets $45.

I am now pretty certain V3 has A-K. That would fit his profile pretty well. Small chance he totally misplayed KK. But I am also thinking he will call if I raise.

The real question is V1. he is way, way deeper than V3. He likes to bluff a lot especially if he smells weakness.

Will he bluff if I just call? Will he call my raise?
Am I even certain V3 will call my raise?

Hero???

Bet turn. I won't comment on river as I saw results. Please stop posting them in your OPs.

Bet turn always.
If you think V1 check/raise bluffs a lot, you give him the chance to check/raise on turn.
By checking turn you ensure the pot is as small as it possibly can be. Which is not great when you have the nuts.
Another reason for betting: If a diamond comes on the river, you may not feel confident enough to raise. Get money in now before a scare card comes.
K.I.S.S. In position always bet when you have the nuts.

I felt like there's very little chance of a flush draw here. V1 would have raised or maybe even shoved with a flush draw. V3 would probably have folded to the preflop bet unless he had 2 broadway diamond cards. Even then he may have folded.

I agree with bet turn always. Has V1 x/r bluffed multi way? With V3? If so, I may be tempted to keep it small and entice a bluff. With V3 leading river, I’d still raise because it’s a big ask for V1 to bluff raise a bet and a cold call. Raising now is easier value.

In that case, I’d consider raising flop.

Bet. The. Turn.

At least 1/2 PSB. On the river, jam. If someone bets before you, jam over it.

How much does V3 have behind, $40?

V1 would basically be bluffing into a dry side pot by raising here with V3 that short. If he’s not a total maniac (your description) he won’t do that.

Checking back turn looks pretty bad to me.

Checking turn is sooooooooooo bad. Like I can't over state how bad it is. If this were a solver output some how, checking turn is a minimum 50bb mistake. Which is a huge number as far as solvers are concerned.

To put that into context it's like calling a 50 bb river bet with 5 high. I'm not exaggerating. You have to bet the turn and try to stack people

Playing hands this way can easily take you from a winning player to a losing player

Raise flop, bet turn, raise river. And as a general rule, stop getting in your own way.