On 8c8d6s we should bet small or check; once we bet and face a 3-bet, KK is strong enough to continue with a call.
Flop 8c8d6s is very favorable for UTG’s opening range, and KK is now an overpair with no real draw. Solver prefers a small c-bet around one-third pot, but checking is also reasonable. The 2bb stab into 7.5bb is a bit too small; a 2.5bb bet (≈33% pot) is preferred.
After we bet 2bb and BB 3-bets to 11bb, we’re getting about 2:1 and need roughly 32.8% equity. KK has around 81% equity versus a typical 3-bet range here, so calling is mandatory. Solver mostly continues with a call, with only a small frequency of 3-bet jamming. Folding would be a huge mistake.