Hard Boiled

Lat sau san taam is a movie starring Chow Yun-Fat, Tony Chiu-Wai Leung, and Teresa Mo. A tough-as-nails cop teams up with an undercover agent to shut down a sinister mobster and his crew.
A cop who loses his partner in a shoot-out with gun smugglers goes on a mission to catch them. In order to get closer to the leaders of the ring he joins forces with an undercover cop who's working as a gangster hitman. They use all means of excessive force to find them.