Fighting Spirit (movie, 1992)

Billy is a young fighter whose sister Judith was hurt after a near gang rape. When he learns she must have surgery, crime boss Russell has Billy compete in illegal street fights. When Billy learns he may get killed, he quits but is later killed by Russell and his men, who were the ones responsible for Judith's accident. After his death, Billy must rely on one man to seek revenge for him: his best friend David. However, David must train in the martial arts before he can seek revenge. Davidy seeks guidance from the ghost of Billy as well as Billy's trainer and ally, Murphy.