This guy was very a LAG player, but i don't know if i should have folded it. What do you guys think. Also play it different on any streets?

PokerStars (9 handed) FTR converter on zerodivide.cx

edit: It doesn't seem to have stack sizes. They were as follows.
Hero: 18950
UTG: 19205

Also, fixed it up, so you know how much he bet at each street, i think that should also be taken into account.

Preflop: Hero is CO with 4:club:, K:club:, K:diamond:, T:diamond:. SB posts a blind of 100.
UTG raises to 400, BB calls.

Flop: 2:diamond:, K:heart:, 5:diamond: (4 players)
BB checks, UTG checks, Hero bets 600, BB folds, UTG calls.

Turn: 7:diamond: (2 players)
UTG bets 1000, Hero calls.

River: 3:spade: (2 players)
UTG bets 2200, Hero calls.

Final Pot:

I call here with 2nd nuts. If villain has AA suited it's bad luck for me.

lovely stuff. I know what you mean, but...

yeah, I pay him off. At first, I thought it reeked of nut flush, but then look at the way he slows right down when the flush hits...betting 1000 on the turn into a pot of over 10,000 (math?) is no way to play a nut flush against an opponent who looks like he's confident in his hand - you bet like you had a set, so he's makin it awful cheap to see the board pair.
If he's got it, he's played it strangely, and fair play to him - he can take my cash. If he hasnt, you take a ton of chips...

Weirdly played hand from your opponent IF he has the nut flush (which I highly doubt based on the way it was played.

Min-raised your flop bet, then called your re-raise. Then, when the flush hits, bets 1000 into a fairly large pot? Doesn't look like the nut flush to me, at all. If your opponent puts you on trips, would he not want you to pay to make a full house to beat his nut-flush? Very risky way to play it on his part IF he does indeed have the nut-flush. :?

Easy call on the river, but I think we are good, so perhaps a raise? 8)

He had A2d for the nut flush.