Personally to find a film scene 'disturbing', it has to grip me psychologically. Recently I watched Ken Russell's The Devils yet again, and I am still disturbed by the scene in which Vanessa Redgrave's Sister Jeanne character is given an enema as the climax to her first public 'exorcism'.
The shots of the men's leering faces as they hold her legs apart, bearing down between them with the giant syringe, intercut with close-ups of her very real looking-and-sounding anguish, make it an extremely uncomfortable experience. Without wishing to cause offence to any real-life victims, I imagine it comes pretty close to what a gang-rape can look and feel like.
I think it's so cleverly done as it's the climax to a scene that starts out fairly quietly and goes on for quite a while drawing you in, then all this hell breaks loose. In amongst all this there's also a lot of absurdist and incongruous comedy going on, heightening the disturbing tone of hysteria.
I find it pretty amazing that scenes like this (and many others throughout the film) were filmed as long ago as 1970, and wonder how much of a smack in the face they must have been to cinema audiences at the time.