This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Big Human On Campus
This fic's version of Youkai Academy is a freakin' nightmare dimension. It doesn't let the reader forget for a moment that everyone at the school is a monster like in the manga/anime, and it shows in many ways:
The students are completely out of control, they murder, rape, curse and do who knows what else to each other on a daily basis.
Many of the teachers are worse than the students, doing the exact same thing but with more freedom and authority. Richard goes of murderous rampages when he's bored, Jaedite disintegrates students for the pettiest of reasons and canon teachers like Hitomi Ishigami are still at large committing vile acts like turning students to stone.
The enforcers, before they were disbanded, were incompetent at best and corrupt, murderous knight templars at worst. They demanded payment from all of the clubs on campus and those who can't pay or refuse are dealt with harshly. The newspaper club and the fight club actively fought against them, but by the time the story begins the enforcers had gotten rid of most of the former and had all of the members (besides Ms. Wildman) in the latter assassinated when classes were finished. They don't really do anything to protect the order and peace of Youkai Academy and actually put in more effort quashing any criticisms directed at them. Any time they actually try to do investigations it shows how unsuited they are for the job, with Kuyo, their leader, actually having to look up the word in a dictionary.
Many of the non-sentient creatures and wild animals around Youkai are very dangerous with the spider infestation being the most prominent. A huge rock-hard spider, larger than any car, actively hunts the students. Ranma was almost eaten by a grue in the boy's bathroom; if he didn't know the moko takabisha, he would have been eaten alive.
Jadeite hints that there are even more mysterious and dangerous creatures and artifacts hidden in the wastes and ruins of the school and his exploration club's goal is to find and use them.
The Headmaster himself, though trying to get the school on track is kind of a dick and makes a lot of questionable decisions like keeping Richard around and inviting humans to bring a little humanity to the school.