A Bittersweet Life

Dalkomhan insaeng is a movie starring Lee Byung-hun, Shin Min-a, and Yeong-cheol Kim. Things go wrong for a high ranking mobster when he doesn't proceed by his boss's orders.
Kim Sun-woo is an enforcer and manager for a hotel owned by a cold, calculative crime boss, Kang who assigns Sun-woo to a simple errand while he is away on a business trip; to shadow his young mistress, Hee-soo, for fear that she may be cheating on him with a younger man with the mandate that he must kill them both if he discovers their affair.