This is easy, The remake of I Spit On Your Grave.
I thought I couldnt be offended by anything, then I saw this movies 20 min rape scene. I have seen other rape scenes which couldnt compare to this one in the slightest. I like the movie besides this part though. On top of that, the lead girl is super hot and it kinda ruins the attraction after seeing her brutally gang raped for 20 mins.