- HD 1080
- Runtime: 120m.
- Status: Released
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- Languages: ko
- Country: South Korea
- Director: Byun Sung-hyun
- Stars: Sul Kyung-gu, Yim Si-wan, Kim Hee-won, Jeon Hye-jin, Lee Kyung-young
- keywords: prison, undercover, undercover cop, gang, bromance, neo-noir, prison release
- Production_studio: CJ Entertainment, Barunson
- Slogan: Careful who you trust.
- The The Merciless is featured in the top rankings of 2017
- #37 in Top Action Movies of 2017
- #40 in Top Crime Movies of 2017
- #16 in Top Mystery Movies of 2017
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.