Have been posting my losing hands looking for a leak.
Here is a winner where I should (?) have won more.

PokerStars 5/10 Hold'em (7 handed)

Preflop: Hero is CO with , .
UTG calls, MP1 folds, MP2 calls, Hero raises, Button folds, SB 3-bets, BB folds, UTG calls, MP2 calls, Hero caps, SB calls, UTG calls, MP2 calls.

Flop: (17 SB) , , (4 players)
SB checks, UTG checks, MP2 checks, Hero bets, SB raises, UTG folds, MP2 folds, Hero calls.

Turn: (10.50 BB) (2 players)
SB bets, Hero raises, SB 3-bets, Hero calls.

River: (16.50 BB) (2 players)
SB bets, Hero calls.

Final Pot: 18.50 BB

Results in white below:
Hero has Ad Ah (one pair, aces).
SB has Kd Kc (one pair, kings).
Outcome: Hero wins 18.50 BB.

When he check-raised me, I guess I shriveled up.
Anyone agree with my passive play here? Because I dont.
I mean what could he have 3 bet preflop, check-raise flop, and have me beat with?
I say NOTHING

I find that except for the maniacs, its rare to see someone 3 bet preflop without AA, KK, QQ or maybe AKs. So the only thing that comes close to beating you on the flop is TT and its unlikely he would 3 bet with it. If he did, then I would either think he's good player trying to isolate you or someone with maniac tendencies (fine line there). So, I would have capped the turn and if he still came out firing on the river, probably just called him down.

I would have likely 3 bet him on the flop but this could be a leak in my game since if I am right, I would be get a lot more out of him on the turn and 3 betting him on the flop could get him to go into check/call mode earilier. I say you probably lost 1 big bet on the turn, nothing else so it wasn't that bad.