Death Machines (1976) on Netflix

Plot summary

Madame Lee presides over a mansion where anyone in town who wants a killing done must come to her. With her assistant Mr. Lu she has three martial arts fighters injected with a drug that leaves them able to do nothing but obey her commands, and she calls them her death machines. A man who stays in the shadows hands her a photograph of Mr. Gioretti, who runs an outdated crime syndicate, and tells her to use Gioretti and his people as the next test. Gunmen around Gioretti begin dying, and he demands to know who is killing them. Frank Thomas studies karate under Hong Lo, one of the men Gioretti wants killed.