Well you may have just witnessed the most disturbing one. Irreversible is horrifying. I saw it in theaters and that scene nearly cleared the room (and it's not like the rest of it was any picnic either). Not much is likely to shock you now, but I'd say Last House on the Left and I Spit on Your Grave come close. Salo: the 120 days of Sodom is also extremely disturbing because the abuse is directed at children. Also, if you'd like to see a man getting raped for a change try Deliverance or American History X. Just a thought.
I don't know about most graphic but I remember seeing rape scenes in The Last House on the Left, Boys Don't Cry, Hounddog (had to skip that one personally, was too much to watch because she's a child), The Girl Next Door...
Oh and I think that "Dead Girl" might of had one too, but I couldn't even finish the movie it was too creepy.. like gross creepy hahahahaha.
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