A Bittersweet Life
달콤한 인생 (original)
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, Heesoo, 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.
Starring Lee Byung-hun, Shin Min-a, Kim Yeong-cheol, Hwang Jung-min, Kim Roi-ha, Oh Dal-su, Jin Goo, Jung Yu-mi, Lee Ki-young, Kim Hae-gon
Watch "A Bittersweet Life" from streaming services Tubi TV, Hoopla, Imdb TV (Prime) and several more released in 2005. It's a action & adventure and crime movie, and has a rating of 7.5 out of 10 from Imdb which is usually fine for this kind of movie.
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Tubi TV