Preflop
I would definitely 3-bet AK blind vs. blind. You are leaving a lot of money on the table by getting into this tricky-trappy game, and you are also setting yourself up to get coolered and potentially lose a big pot. If he fold to the 3-bet, thats a totally fine outcome. You win a 4BB pot assuing a 3BB raise from him, which is more, than AK is going to win on average.
Flop
Definitely betting for value on this board, but I think, just 30% pot is leaving money at the table at 2NL. When he check-raise you, I would just call though, since he can certainly have QQ or KQ, and I want to keep his bluffing range alive.
Turn
Turn is a complete brick, and he check to you. Its always a little weird, when someone takes this line. Is he slowing down with a draw or trying to go for a dubble check-raise? However there are so few combos, you lose to (3 KQ and 3 QQ), so I would put in a bet for value and protection.
River
Another blank and now he blast all in for 5-6 times the pot. I dont think, 33 or 22 check-raise the flop. So you still only lose to those 6 combos of KQ and QQ, which had you coolered the whole time. Maybe some K3 or K2 as well, but those hands are quite unlikely, that he raised preflop. Ranges are wide blind vs. blind, so I think, you have to close your eyes and call it off.
Results
No idea what he was doing with K9, but it just goes to show, why you cant fold a hand this high in your range to a line, that makes little sense, and especially not at 2NL. If he has it, he has it, and then you just reload and play on.
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