This literally was the first or second hand of the tournament.

Blinds: 100/100
Effective stack: 20K (level 1, very early)
Position: HJ
Hand: Kc9c

Pre-flop:
Folds to Hero who bets 300 from HJ
CO folds
BTN (50+ European player, no reads) 3-bet to 800
SB folds
BB (30-ish American, no reads) calls 800
Hero calls

Flop - Pot (2.5K): Kd9d3d
BB checks
Hero checks
BTN checks

Turn - Pot (2.5K): Jh
BB quickly bets 4K
Hero calls 4k
BTN folds

River - Pot (10.5K): 3c
BB snap jams for 15K
Hero ?

On river it doesn't seem like we beat anything that bets for value, but is our hand a decent enough bluff-catcher to even consider calling off when we block some boats and the only better 2 pair other than trapped AA? If it's a fold what does our calling range look like?

KJ is also better. IME people aren’t bluffing off a 1K on first hand of the event. I’d let this go.

I would rule out AA for BB. Mostly they would raise pre-flop rather than see the flop 3 ways OOP.

So the hands we lose to are flopped flushes/QT/KJ/JJ/99/33. I think QT have less combos than the max because BB would fold the non-suited ones some of the time. Also BTN may have QQ/TT some of the time reducing combos.

Having said that, I don't think BB is bluffing much here. Hero can have a flopped flush or QT or even KJ.

So I would fold. Villain would have to be bluffing like 35% of the time for us to break even calling. With most likely the A. Could be a hand like A/X where X is a Q, J, T. But I don't think these bluffs add up to 35% of the total hands that would be betting like this.

OTT V over-bets the pot by 1.5K - so maybe looking to set up the river shove if called. I don't see this line as a bluff very often. Good fold.

Question - if we believe it's a fold, what are we calling with here? Is it just A-high/Q-flushes and boats, maybe KJ with the Jd if I really want to bluffcatch? (if I even call the 3-bet with KJo)

I'm not even sold that a straight is particularly great here unless we have a diamond blocker and I might not be opening QTo from the hijack, and if I am, it might be far enough down in my range that I fold to the 3-bet. And a 3-bet cold call range is going to most of the of big card flushes that I would be crushed against if I decided to call off with weaker flushes, so I'm not even sure something like JdTd or Td8d (if I even have that in my range) are hands I would want to call here with.

I think I'd only be calling flushes and better here. K9 seems like a pretty easy fold.

Just for the record, I did fold after some thought. Villain didn't show, but the original 3-bettor claimed he folded TT with the ten of diamonds on the turn. The villain turned out to be something of a maniac so it's possible he was over-bluffing there, but no way to know that on the first hand of the day.