Naked Massacre (1976)
A Vietnam veteran, alone in a troubled Belfast, has nothing good going on. He happens upon a house where eight nurses live. He torments, rapes, and murders them. This is a disturbing low budget movie, not disturbing in the usual horror movie way, but disturbing in a mean ugly way. Making it even more upsetting is the fact that it's a true story based on the Robert Speck murders.