The Six Thousand Dollar Nigger aka Super Soul Brother 1978

A homeless man is injected with an experimental drug that gives super human strength. What he doesn't know is that the doctor who's doing the experiment is a criminal, trying to create an unstoppable thief that's immune to bullets. Steve gains all the powers that Superman has, and after getting his revenge against all those who harassed him on the street, discovers the truth about the doctor's plans for him.