Psychologically disturbing book rec

Now that anime are on the rise, most ppl would probably know bungo stray dogs. And one if the biggest authors from the series, is really loved. He is Osamu Dazai.

Mostly I've been searching for extremely devastating FICTIONAL reads about the human psyche/mental mindsets and preferably what happens if they are not kept in check.

Here are some books that I like and will fit the theme:
No longer human by Osamu
Earthlings by Sayaka Murata
Less than zero by Brett Easton Ellis

Tldr: recommend a book similar to no longer human which is not entirely non-fiction. (No rape books)

Thanks in advance, I'll be reading all your comments.