What's the most 'extreme' movies you have watched ?

Extreme to you, so doesn't necessarily need to be gory or scary just whatever you found stuck with you. For example I will never forget eden lake, that really messed with my head. There was also a movie I watched where the opening scene was a teenager who was forced to r*pe his mum and continued to keep going after they killed the mum.. I can't remember the name and I think the rest of the film was pretty crap but that opening scene was definitely extreme. For me martyrs wasn't bad, I dunno I never found it that extreme or anything, I can barley remember it that's how much it didn't bother me. What are your guys movies you won't forget ? (They don't need to be good films)