Righteous Ties (2006) on Netflix

Plot summary

Dong Chi-sung is an eccentric but faithful gangster who has served his organization for a decade. A stabbing done at his boss's instruction puts him behind bars. While he is locked up, a rival mob attacks his parents, and the gang he has given his life to takes no action. That silence convinces Chi-sung that his years of service have bought him nothing, and he decides to confront his boss and looks for a way out of the prison with other inmates. His childhood friend Kim Joo-joong is handed the job of stopping him, and the assignment leaves him choosing between his friendship and his place in the gang.