History NightmareFuel / AssassinationClassroom

* ''The flippin' principal.'' [[DeanBitterman Asano Sr.]] is not right in how he treats everyone - including his own son - callously, and that centipede motif of his... When he completely snaps, this gets ramped UpToEleven. He moves to destroy the Class E Building '''''WHILE CLASS E IS STILL INSIDE OF IT''''', intends to move them to a new school building that should just be called a HellholePrison, and announces his intent to fire Koro-Sensei. To reiterate, he just stated that he intends to completely terminate Class E, the only thing stopping Koro-Sensei from destroying the world. And all of that is because Class E and Koro-Sensei have proven his educational model does not work. And this is mild compared to what he's done to some other people. Remember that bum Asano gave some money to? That was one of the boys who bullied one of his students and drove the student to suicide. Really makes you realize just how badly Asano was affected by the student's death. He could've used all his intellect to simply kill them and make it look like an accident. Instead? He got them hopelessly addicted to gambling, robbed them of any particular drive except to gamble, and ruined their lives so that they became dependent on the allowance he gives them. Really puts a lot of other things into context. Do not make Asano mad by harming the people he cares for.

* The "God of Death". He's capable of disguising as anyone, or even anything, as shown when he attacks a hitman after (seemingly) emerging from his own shadow. And if you need more proof, his camouflage skills are so high he appears in front of the students without disguise as an humanoid silhouette with only his two eyes glowing like a pair of spotlights. He even skinned his own face to improve his disguises. Yet, somehow, his hair, eyeballs and everything else remain in place, even though he's got no facial muscles anymore! [[Film/TheDarkKnight Forget Two Face]], this guy is even scarier! And then there's his "Death Scythe", a small, hidden gun inside his index finger. This guy can kill you just by doing a single "Bang!" gesture. This is when CrazyAwesome is mixed with a villain hitman.

* Nagisa's mother, full stop! The woman sees Nagisa as an extension of herself, dictating where he'll go in his future and what job he'll have simply from what she wanted and failed to achieve in her youth. What makes this worse than a typical StageMom situation is that she denies Nagisa's own gender, forcing him to keep his hair long (hence his pigtails) and even makes him wear dresses to give him "advice" on how to dress in the future. Whenever he shows the slightest deviance from her plan, she flies into a rage and attacks him, emotionally blackmailing him into going along with her. You know how Nagisa's so good at reading and observing others? That's why. This is made all the worse when, instead of questioning why he wants to stay in E class, she decides the most logical route is to drug him, drive him to Class E at night, and then ''set fire'' to the building so he'd be forced to beg the chairman to let him in to the school again! If it weren't for an assassination attempt, things could have gone very hairy indeed. In other words, the appearance of a murderous hitman made the situation ''less'' scary.

Even though this is a Shonen Jump manga published alongside the likes of ''Manga/OnePiece'', ''Manga/Bleach'' and ''Manga/Naruto'', make no mistake: there's enough Nightmare Fuel to fill a whole classroom. Heck, it wouldn't be a Shonen Jump title without this trope.