Brutti, sporchi e cattivi / Ugly, Dirty and Bad (1976)

Four generations of a family live crowded together in a cardboard shantytown shack in the squalor of inner-city Rome. They plan to murder each other with poisoned dinners, arson, etc. The household engages in various forms of sexual idiosyncrasies, land swindles, incest, drugs and adultery.

Imdb