Another vote for Watership Down. That movie...shit...I had nightmares about it like no other film has ever caused in me since and even at the age of 37, I still really don't like it.
I thought the Antichrist movie was a bit dull myself and I am wracking my brains trying to think of which bit has bothered people (I'm assuming the bit where she cuts off part of her genitalia?). But then gore/graphic violence really does not bother me. Put it this way:
In the early days of cinema, people would rub screaming from footage of what they perceived as a train coming towards them. Then they became a little more sophisticated and understood what they were looking at and it stopped being so frightening.
That is kind of how I feel about violence in films. Am I desensitised? Perhaps. But I understand that what I am looking at is prosthetics and bits of rubber and fake blood, or CGI, or camera trickery. None of it is ever real and because I know that, it really is a non-issue for me. I think it manifestly unlikely that any scene of cinematic violence will ever "mess me up". At best it is a good performance by a screaming actor. At worst, I know that when "cut" is called, people simply stand up and walk away as if nothing ever happened because, well, nothing happened.
Of course, Watership Down is not real either. But the themes, and perhaps the memory of how much it upset me as a kid, are still troubling (probably the later).