Aria, the main character of Dead Girl's Notebook, is a depressed gay masochist who often speaks about herself in cruel and dehumanizing ways and sometimes fantasizes about dying. (Aria, the real person who is writing this, is doing okay lately.)
There's a consensual BDSM sex scene where Aria is subject to various humiliating and painful things. Humiliating kinky "punishments" come up in other parts of the story in a comedic context.
There are a handful of scenes involving damage to the body, such as characters bleeding or losing limbs.
You can view a more detailed breakdown of content warnings per chapter here.