The Merciless

Bulhandang is a movie starring Kyung-gu Sol, Si-wan Im, and Kyeong-yeong Lee. A young cop finds his loyalties divided after befriending a notorious criminal while undercover in prison.
Jae-ho, who aims to become the number one in a crime organization, gets to build up trust with Hyun-su, an ambitious newbie in the prison. While they try to take over the organization after the prison release, their ulterior motives starts to emerge.