Preflop and flop are fine; the big leak is not barreling turn in a 3-bet pot, which leaves us in a tough river bluff‑catch spot.
Flop 7s 8d 4h in a heads-up 3-bet pot with SPR ~4.2 is pretty favorable for the 3-bettor: we keep a clear overpair advantage, while UTG has more medium pairs and suited connectors. Betting 9 into 21.5 (~42% pot) is a good, efficient c-bet size with KK—strong enough to start building a pot and deny equity from hands like 99–TT, 66, AQs, 9T/QJ, but small enough that our overall range can bet frequently. Checking here would be fine as a mix, but betting is comfortably standard.
Turn Ts makes the board more dynamic (now straights like 65 are there and we pick up more straight draws like 96/J9), but in a 3-bet pot with KK, SPR ~2.7 and pot 30.5BB, our hand is still in very strong shape versus UTG’s likely calling range (88–JJ, 99/TT, some 7x/8x suited, a bunch of AQ/AJ/KQ type floats). The key strategic idea: with this SPR, our default with overpairs is to keep betting and cleanly define our value/bluff ranges—checking concedes initiative and lets UTG realize equity with hands that would have to fold or pay again. A solid line here is to barrel something like 18–22BB: we fold out high-card floats, charge draws (J9, 96, 65 if somehow peeled), and get value from 88–JJ and some sticky Tx/8x. By checking back, we protect our stack but sacrifice EV and allow UTG to realize equity and turn their range into well-protected river bets.
Note: Checking back turn with an overpair in a low SPR 3-bet pot surrenders initiative and lets UTG realize too much equity; a strong second barrel is higher EV versus their capped flop-calling range.
River Ad is one of the worst cards in the deck for KK: a lot of UTG’s flop-call/turn-check range contains Ax (AQ/AJ suited, sometimes AK slowplays) that now beats us, and draws like J9/96 can also choose to bluff. Facing 20 into 50.5 (~40% pot), we need ~28% equity to call. In theory, KK will often be mixed here as a bluff-catcher, with better calls coming from KK with an ace-blocking effect or from hands that block more of Villain’s value range. With our line (under-repped by checking turn but now facing a river lead on a brutal card), folding is very reasonable exploitatively—especially in typical cash games where UTG is under-bluffing this exact node. The real issue was giving up the turn; once we arrive here, folding KK to the river stab is not the big leak.
Note: River fold with KK getting good price is slightly tight in theory, but given the A river massively favors UTG’s range and population under-bluffs, it’s a small if any mistake compared to the missed turn barrel.