Possession (d. Andrzej Żuławski, 1981)

If you could somehow distill pure not-from-concentrate Divorced Guy Energy and pour it onto celluloid, you’d get something that vaguely resembled Possession. It takes a particularly fucked up, jilted mind to take a film about a marriage dissolving to where this goes, to say nothing of how disjointed and coldly malevolent it turns out.
James Sunderland got off light. His wife getting a wasting disease and becoming an angrier, more hostile version of herself is one thing. Sam Neill’s Mark is married to a woman (Isabelle Adjani) who leaves their young child neglected in an apartment for hours on end, has a random collection of dismembered body parts in a fridge in a separate apartment across town, had what can only be described as a full-body miscarriage in a subway station, and is apparently having the most incredible sex of her life with a murderous tentacle creature. Mark responds by getting involved in seething, violent arguments with her that end in murder and hate sex. Raise your game, Mary Sunderland.