Hello, I've been trying to find a name for a specific subcategory of guro. If this topic upsets you please do not read ahead, as I do not know how to spoiler text.

What's it called when someone gets their brain physically fucked with to become a mindless sex drone? I've been searching many keywords and foud nothing.

What you're looking for is probably the brain_injection tag, there's also the brain_fuck tag on sites like e/n-hentai

They don't always imply some sort of mind control or alteration though, it could just as easily be a snuff thing where someone has intercourse with a brain (with the obvious consequences)