I'm trying to find a movie that I watched on cable (HBO, in the US) in 1980 or 81 when I was a kid. It was a thriller, very violent with a fair bit of nudity and a couple of very violent scenes:
A couple have sex in a small room with little furniture and vertically striped wallpaper. It was like a doctor's exam room or similar. After sex, the man beats the woman to death by crushing her skull.
The same man (I think) beats another woman at a big open apartment. In the struggle an aquarium is broken and he decapitates her on a big triangle of jagged glass sticking up from the aquarium. He wraps her body in a rug and carries her out.
I was only 12 when I saw this, and those are the only 2 scenes that I remember. It was in color and in English. I don't remember what the man looked like or much else