Honestly? I won't know what I will not write until confronted with the notion of it (if that makes sense). I've written a pretty wide variety of things, when the story calls for it.
I have dealt with rape. One character was raped as a teenager, and relived those memories later as an adult. It was not explicitly written, but still relived on-screen. I don't know if I could write an explicit, detailed rape scene. I've never had the need.
I have dealt with torture, on screen and off. Some explicit, some not. I don't really have a problem with violence in my writing. My betas will tell you that I love to beat on my characters (pent up personal aggression? Dunno....). I've had them shot, stabbed, beaten, electrocuted, tossed down stairs, smashed beneath falling debris, caught in fires, inhaled chemicals, nearly suffocated, drowned, etc...
I've never written the graphic torture-leading-to-death of a character. I probably would, if it became necessary. Again, because that sort of graphic physical violence squicks me less than graphic rape.
I've written semi-explicit sex scenes. Many of them are blow by blow (no pun intended) encounters, but I prefer to use "nicer" language. I'm not fond of words like c*ck or p*ssy and won't use them. But I am careful that I don't fall overboard with the euphemisms (pulsing staff and hot tunnel just don't work for me, either, ugh).