Sick Runout Versus A Reg

Hero (not me): Former accomplished tournament pro before COVID who has been crushing the 5/5/10 capped and bounty NLHE games post-COVID. One of the biggest winners in the player pool. Perceived to be Semi-LAG and sticky versus aggros.

Villain: Serious rec small winner at 5/5 NLHE pre-COVID. Has become one of the biggest winning regs in the 5/5/10 capped and bounty NLHE games post-COVID. Very capable of unloading the clip on big bluffs.

Blinds 5/10/20 with bounty (whoever wins 2+ hands in a row receives $25 from each other player at table). Bounty player (guy who won the previous hand) folds. Folded to Villain who open-raises $105 from CO. Hero flat-calls red 75 offsuit in the 5 blind. Other blinds fold out.

Heads-up Flop: K55r. Hero checks. Villain cbets $75. Hero CR to $225. Call.

Turn: badugi 3 completed rainbow. Hero bets $400. Villain calls.

River: Kx. Hero checks. Villain thinks for 5 seconds and overbet shoves $1.8k.

Hero?