This is a live-action example but literally anyone from Stranger Things. I preemptively put it in my blacklist and found out there isn't much on this site anyway, but the combination of much of the cast being underage and the reality that some of that R34 probably involves the show's monsters makes me never wanna see any of it. I have yet to stumble upon any and hope I never do.
Also, less distressing example, but Harry Potter. It's more to do with personal tastes and how I view the series in this case, but I wouldn't be disturbed unless it was something really egregious like Voldemort raping Hermione or something.