Riki-Oh: The Wall of Hell (1989)

The story of a young man with the strength of 50 men who finds himself inside a harsh prison run by an evil assistant warden and the head boss who secretly has the ability to transform himself into a "Hulk" type monster. Riki, who is also secretly on a quest to find the hidden opium garden the prison warden has been growing, will learn something about himself that will change his life forever.