I have my limits to what I will watch when it comes to "extreme" but I will never not watch something fictional due to content and prefer to look away for a scene if it involves any of the few things I can't handle. For me, these would be animal torture and almost anything to do with abuse or murder of children.
I do seek out crime scene photos and have seen the worst of the worst. I have seen many crime scene and autopsy photos of children, I don't seek them out but oddly they don't bother me as much as watching a fictional child character being abused. Perhaps it is because watching the event take place evokes a sympathetic response and seeing an already dead child means they are no longer in pain.
I also (and I know for some of you this may be hard to understand and may even make you think less of me) seek out videos of actual, real life beheadings and deaths. I know how fucked up that sounds. Beheading has both fascinated and scared the living shit out of me for years. I have always been insanely obsessed with that last moment, wondering how long the brain functions after the head is removed from the body. This is the one way I am most afraid to die. I have sympathy and feel empathy for the victims and it is NOT easy to watch but it oddly eases my fears in a way that nothing else can. That being said, I could never watch a real video of a child beheading or murder of any type, nor will I watch any real video of animal torture or murder.
So what are your limits?