Defending K6o pre is fine, but ripping it on 987cc versus a UTG c-bet is too loose—small raise or call is better.
Flop comes 9s 8c 7c and we’ve got an open-ender plus a backdoor diamond draw on a very connected board. UTG has a slight range advantage, so checking our entire range, including this hand, is the standard approach. If we do decide to bluff-raise, a smaller size around 7–8BB works better than jamming; the shove just isolates us against very strong hands and folds out the weaker stuff we’re targeting.
After we check and UTG bets 3.2BB into 5.25BB, we’re getting about 2.6:1 and need roughly 27% equity; K6o has around 36% versus UTG’s c-betting range, so we’re well ahead of that threshold. The problem is that UTG’s calling range is very strong here—mostly 9x, 8x, 7x, sets, and strong draws—while the hands that fold are the weaker ones we’re trying to bluff. A small raise to around 7–8BB would be a better way to pressure those weaker hands without committing our stack; the shove is just too ambitious with this combo.
Note: Jamming K6o on 987cc versus UTG’s c-bet is too loose; a small raise or call is higher EV.