SB is a fish, 54/5 over 61 hands cold calling alot of 3bets.
It seems kind of gross to fold this against someone who probably has 50% of ATC into the flop but I just couldn't think of any hands he could be bluffing here, and fish do like taking this weird lines with nutty hands and I think 99, 88, 55, JTs, 98s, 76s and Q9s are all probably in his range and when he gets to the river with worse it's usually with some sort of weak made hand which he rarely, if ever, donk shoves as a bluff.
Poker Stars $100.00 No Limit Hold'em - 6 players - View hand 1738171
DeucesCracked Poker Videos Hand History Converter
Hero (MP): $228.81
Pre Flop: ($1.50) Hero is MP with K K
UTG raises to $3.50, Hero raises to $10, 2 folds, SB calls $9.50, 1 fold, UTG calls $6.50
Flop: ($31.00) 9 5 8 (3 players)
SB checks, UTG checks, Hero bets $18.00, SB calls $18, UTG folds
Turn: ($67.00) Q (2 players)
SB checks, Hero bets $36.00, SB calls $36
River: ($139.00) 2 (2 players)
SB bets $83.98