The Killer: A Girl Who Deserves to Die (2022) on Netflix

A retired hitman agrees to take care of a teen aged girl, but when she becomes involved with unsavory people, he has to rescue her.

Ui-gang is a hit man who has decided to retire. He has a nice house and all the money he needs, but one day his wife takes a trip to Jeju Island and leaves him with a request. Her companion on the trip has a 17-year old daughter Yoon-ji who will be left alone during their three week vacation. Ui-gang reluctantly agrees to look after Yoon-ji and make sure she doesn't get into trouble. But she does get into trouble. Yoon-ji is not a bad kid, but she makes some poor choices, and before she realizes it, she finds herself in a situation far more dangerous than she ever imagined. But just as Yoon-ji is in over her head, her captors too will find themselves with more than they can handle when Ui-gang shows up to take her home.

—Darcy Paquet