The Perfect Weapon (movie, 1991)

Jeff, a young delinquent, is enrolled by his father in a kenpo school, in the hopes of teaching the boy some self-discipline. Years later, Jeff's mentor, Kim, is being threatened by one of the Korean mafia families. Jeff tries to help his old friend, but is too late to prevent Kim's death at the hands of an unknown hitman. Vowing revenge, Jeff takes on all of the families, using his martial arts skills to find the man who killed his friend.