Mercy for None

In his past, Nam Gi-Jun (So Ji-Sub) was a member of the Bongsan Gang that was led by Gu Bong-San (Ahn Kil-Kang). Nam Gi-Jun defeated other gangs through violent battles and the gang grew into a large company, but Nam Gi-Jun decided to leave the gang. His younger brother Nam Gi-Seok (Lee Jun-Hyuk) joined the Joowoon Gang that was led by Lee Joo-Woon (Heo Jun-Ho). The two gangs were rivals. For his brother, Nam Gi-Jun quit the Bongsan Gang by cutting his left Achilles tendon. 11 years later, Nam Gi-Jun lives peacefully and makes a living by suppling drinks to businesses run by Bongsan. His brother Nam Gi-Seok is now the second highest ranked person in Joowoon, but he suddenly dies. In order to reveal the secret behind Nam Gi-Seok’s death and take revenge on those responsible, Nam Gi-Jun goes back to the gang world that he left behind 11 years ago. Source: AsianWiki