Infernal Affairs (2002)

Ko Chow is an undercover cop who is under pressure from all sides. His boss, Inspector Lau, wants him to infiltrate a gang of ruthless jewel thieves; his girlfriend wants him to commit to marriage or she will leave Hong Kong with another lover; and he is being pursued by other cops who are unaware that he is a colleague. Chow would rather quit the force, feeling guilty about betraying gang members who have become his friends.

Something fishy is going on in the anti-Drug Trafficking Unit of the HK Police, and only a few honest cops know that the corruption goes all the way to the top. However, they must prove their case quickly, and by unconventional means, after they are framed for murder and drug-trafficking themselves. Dodging bullets from cops and criminals alike, the race is on to clear their names, protect their loved ones, and bring their corrupt colleagues to justice.

A police detective's investigation of a prostitute's murder points to his best friend.

Cheung Sung-bong is a highly respected cop with a long history of success in dangerous cases. However, his past soon comes back to haunt him when a former protégé resurfaces, seeking revenge.

Hoping to raise enough capital to finance a legitimate business and leave behind his life of crime, Liverpool underworld boss Ged Brennan sends his brother Ratter and a crew to pull a daring final heist. But when Ratter kills a drug kingpin during the job, Brennan must turn to rival crook Franner to avert an all-out gangland war.

Liu Yue Ping reports to the ICAC about a rich 2G Cao Yuen Yuen who bribed officers of the Hong Kong Correctional Services (HKCS) from inside the prison. William Luk decides to infiltrate the prison as an inmate to conduct his investigation, while his partner Ching Tak Ming and Chief Inspector Lau Po-keung back him up from the outside.

A financial tycoon, once a triad member, tries to eradicate the drug market while an old accomplice aims to be Hong Kong's first drug lord.

An undercover cop struggling to provide for his son and ailing wife, must infiltrate a ruthless gang. But things turn sour when another cop blows his cover and he quickly finds himself battling for his life and the lives of his family.

Two detectives who are up to their necks in trouble and in each other's face, as they try to shut down a drug-trafficking scheme that could be connected with international ties to organized crime. But in the midst of their investigation, innocent immigrant dock worker Luk Wan-Ting gets caught up in the mix when he witnesses the murder of an intelligence operative and is framed for the crime.

A special agent has for 8 years been deep undercover in Asia's lucrative organized crime trade as he plays protégé to one of the key players, Banker. Now, Nick has but he has started to feel loyalty to his new environment and to the money.