Sins of the Flesh (Les charnelles) (1974)

Benoit has been driven to voyeurism and impotence due to having a cold, treacherous industrialist as a father and an exhibitionist aunt who constantly parades around nude. Jean-Pierre is a thief. Isabelle is a runaway whose stepfather tried to rape her. When the three cross paths, criminal activity, rape, madness and murder follow in this psycho-drama filled with soft-core sex.