Soo (2007)

The title of the film comes from the protagonist's name Tae-Soo (Ji Jin-Hee). He has a twin brother Tae-Jin (also played by Ji), with whom he roamed around the fish market 19 years ago. One day, Tae-Soo tries to steal from a gang who end up catching Tae-Jin for the crime instead, leading to the brothers' separation. While Soo becomes an efficient mob fixer/assassin who is hated by police and rival criminals alike, Jin becomes a police detective, even though he once worked for the gang Soo stole from. One day, a mysterious call leads Soo to Tae-Jin, but just as the two brothers lock eyes and get ready for some brotherly bonding, Tae-Jin is killed. Overwhelmed equally by grief and rage, Tae-Soo sets himself on a straight line of revenge by doing whatever it takes to find his brother's killer, including impersonating Tae-Jin to infiltrate the police force. Then again, Tae-Soo doesn't have to do too much to find the killers, because the gang, thinking that he's Tai-Jin, intends on finishing the job they believe they failed to accomplish