Penitentiary: The Trilogy

Penitentiary I (1979)

Penitentiary II (1982)

Penitentiary III (1987)

imdb.com:

The groundbreaking trilogy depicting the harrowing prison existence of a convict who uses his wits and fists to survive. Martell "Too Sweet" Gordone is thrown deep into the bowels of the prison system, where the only consistent truth is kill or be killed. To show his strength and gain respect from the other inmates, Gordone (Leon Isaac Kennedy) must distinguish himself as a boxer, taking on all comers to save his own skin and regain his pride as a human being. Surprisingly effective in its harsh detailing of violent prison life, the film addresses the dehumanization of prisoners without excusing their crimes. Thought of as an exploitation picture, Penitentiary rises above its roots to provide a blunt and passionate look at one man's struggle on the inside. --Robert Lane