History NightmareFuel / AssassinationClassroom

Even though this is a Shonen Jump manga published alongside the likes of ''One Piece'', ''Bleach'' and ''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.

** While [[AssholeVictim thoroughly deserved]], we also have Takoaka being defeated by Nagisa again and just ''snapping'' completely, first through a FreakOut of epic proportions as he sees Nagisa smile at him once more, and then through going totally catatonic as he is carried away on a stretcher, wrapped in a straightjacket.

* For starters, the Assassination Classroom's own nonhuman professor, Koro-sensei. Imagine having a strange creature as a teacher. Now imagine that under his cheerful facade, you know that whatever he is, he's ''immensely'' powerful and can (and will) destroy the entire planet in one year, unless he's dead. And the first proof of his power? Thanks to him, about 70% of the moon has been defaced, turning it into a permanent crescent. And he's very hard to kill, if not impossible. Normal bullets don't work on him, and he can reach Mach 20 easily [[note]]Yes, 20 times the speed of sound, almost 7km per second and enough to reach low orbit[[/note]]. Luckily his weak point (some substance which can be used for [=BB=] pellets and knives) is revealed from the beginning, but good luck trying to kill him with it.

* Pitch Black: Furious. Koro-Sensei truly angry is terrifying, in both appearance and intent. In five seconds he gathers the name plates of his students and all of his students friends and family from their houses. He knows where everyone lives. He gave his word that he wouldn't harm any of the students, but if he wanted, he could kill ''anyone'' else. There's nowhere to hide.

* For starters, the Assassination Classroom's own nonhuman professor, Koro-sensei. Imagine having a strange creature as a teacher. Now imagine that under his cheerful facade, you know he can (and will) destroy the entire planet in one year, unless he's dead. And the first proof of his power? Thanks to him, about 70% of the moon has been defaced, turning it into a permanent crescent. And he's very hard to kill, if not impossible. Normal bullets don't work on him, and he can reach Mach 20 easily [[note]]Yes, 20 times the speed of sound, almost 7km per second and enough to reach low orbit[[/note]]. Luckily his weak point (some substance which can be used for [=BB=] pellets and knives) is revealed from the beginning, but good luck trying to kill him with it.

** Some context for what causes Karma to notice Nagisa's bloodlust. A little bit before Karma envisions Nagisa's bloodlust, Karma goes to look for the table Nagisa is sitting at (in the scene, which is set before the series begins, Karma and Nagisa are eating at a fast food joint) and it's Nagisa's rather innocuous attempt of getting Karma's attention that causes Karma to notice Nagisa's bloodlust. What actually happens is that Nagisa taps Karma's back to get his attention. What Karma seemingly perceives to have happened is, in a similar style to how the snake motif is presented, a silhouetted version of himself is shown being ''stabbed in the stomach with a katana!'' [[https://imgur.com/4pg1CMD Here's a picture of that by the way]]

* During the final battle with the God of Death, Kayano lunges at him to land a blow, only to get ''impaled'' by one of his tentacles. At this point, we finally see [[BerserkButton Koro-sensei's reaction to one of his students being hurt like this]]. Yes, he gets angry, but his standard black-coloured anger won't cut it here. He gets so, so much more enraged than he's ever been ''[[UnstoppableRage that he completely ignites into a blinding-white glow with a red BattleAura, roaring his lungs out the whole while]]''. Sure, he's able to harness it into a battle-ending explosion, but seeing ''Koro-sensei'' - a kind-hearted and empathetic teacher who loves each and every one of his students - '''''that''''' flaming pissed is jarring indeed.

Even though this is a Shonen Jump manga published alongside the likes of ''One Piece'', ''Bleach'' and ''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.

* For starters, the Assassination Classroom's own alien professor, Koro-sensei. Imagine having an alien as a teacher. Now imagine that under his cheerful facade, you know he can (and will) destroy Earth in one year, unless he's killed. And the first proof of his power? Thanks to him, about 70% of the moon has been defaced, turning it into a permanent Crescent Moon. And he's very hard to kill, if not impossible. Normal bullets don't work on him, and he can reach Mach 20 easily [[note]]Yes, 20 times the speed of sound, almost 7km per second and enough to reach low orbit[[/note]]. Luckily his weak point (some substance which can be used for [=BB=] pellets and knives) is revealed from the beginning, but good luck trying to kill him with it.

* The Principal. Asano is not right in how he treats everyone, including his own son, callously and that centipede motif.... 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 end the Class E completely, which is 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.
* Six words: [[WhamLine "I love you, Koro-sensei. Now die."]] Kayano then reveals she has a set of black tentacles on the nape of her neck. Not tentacles doubling as hair, like Itona, but black tentacles connected right to the nape of the neck. Then, when the first attempt is unsuccessful, Kayano meets Koro-sensei for what is essentially a SuicideAttack[=/=]SelfDestructiveCharge. But that's not the creepy part. She's sweating so much she looks sick, looks more and more deranged the longer the fight goes on, and is explicitly stated to be losing her mind.
* How Koro-sensei got close to the woman in his flashback. He was captured to be used in an experiment and she was the one who interacted with him personally through a pane of reinforced glass. That's not the scary part: the scary part is that the head doctor, her fiance, knows that if Koro lost control or became too enraged, his new powers would enable him to get through that glass and kill her with ease. The doctor even outright calls her a potential sacrifice! She was close to him because the other researchers wanted someone expendable in that position.

* During the final battle with the God of Death, Kayano lunges at him to land a blow, only to get run through by one of his tentacles. At this point, we finally see Koro-sensei's reaction to one of his students being hurt like this. Yes, he gets angry, but his standard black-coloured anger won't cut it here. He gets so much angrier than he's ever been, ''that he ignites into a blinding-white glow with a red BattleAura, roaring his lungs out the whole while''. He's able to harness it into a battle-ending explosion, but seeing Koro-sensei that flaming pissed is jarring indeed.

* During the final battle with the God of Death, Kayano lunges at him to land a blow, only to get run through by one of his tentacles. At this point, we finally see Koro-sensei's reaction to one of his students being hurt like this. Yes, he gets angry, but his standard black-coloured anger won't cut it here. He gets so much angrier than he's ever been, ''that he ignites into a blinding-white glow with a red BattleAura''. He's able to harness it into a battle-ending explosion, but seeing Koro-sensei that flaming pissed is jarring indeed.

* For starters, the popular alien. Imagine having an alien as a teacher. Now imagine that under his cheerful facade, you know he can (and will) destroy Earth in one year, unless he's killed. And the first proof of his power? Thanks to him, about 70% of the moon has been defaced, turning it into a permanent Crescent Moon. And he's very hard to kill, if not impossible. Normal bullets don't work on him, and he can reach Mach 20 easily [[note]]Yes, 20 times the speed of sound, almost 7km per second and enough to reach low orbit[[/note]]. Luckily his weak point (some substance which can be used for [=BB=] pellets and knives) is revealed from the beginning, but good luck trying to kill him with it.

* During the final battle with the God of Death, Kayano lunges at him to land a blow, only to get run through by one of his tentacles. At this point, we finally see Koro-sensei's reaction to one of his students being hurt like this. Yes, he gets angry, but his standard black-coloured anger won't cut it here. He gets so much angrier than he's ever been, ''that he ignites into a blinding-white glow with a red BattleAura''. He's able to harness it into an EmotionBomb, but seeing Koro-sensei that flaming pissed is jarring indeed.

* [[FinalBoss The Final Question]]. It may seem out of line compared to most of these examples, but consider it from the position of a student. It's the end of an incredibly hard series of exams, you're completely exhausted but there's no stopping because you don't know how far everyone else will go, and then this thing shows up. It's a college-level geometry problem, miles above the level of anything that came before, intentionally worded in an extremely confusing way, and it's worth ''a fifth of your grade in that subject''. Is there any worse nightmare for a student? Fortunately, there's an easy way to intuit the answer, and there's no need to show your work.

* The fact that, in a span of a school year, Korosensei raised an [[ChildSoldier entire class of assassins]] that are just as capable as he is in his prime.

* 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.

* Koro-sensei's transformation is grade-A body horror in chapter 139.

* For starters, the popular alien. Imagine having an alien as a teacher. Now imagine that under his cheerful facade, you know he can (and will) destroy Earth in one year, unless he's killed. And the first proof of his power? Thanks to him, about 70% of the moon has been defaced, turning it into a permanent Crescent Moon.
** And he's very hard to kill, if not impossible. Normal bullets don't work on him, and he can reach Mach 20 easily [[note]]Yes, 20 times the speed of sound, almost 7km per second and enough to reach low orbit[[/note]]. Luckily his weak point (some substance which can be used for [=BB=] pellets and knives) is revealed from the beginning, but good luck trying to kill him with it.
** Lets just say he could just as easily destroy the earth and everyone in it. Be lucky he's affable.

* And don't forget the "God of Death", the closest thing to a human EldritchAbomination. He's capable of disguising as anyone, or even anything, as shown when he [[spoiler: 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 [[spoiler: an humanoid silhouette with only his two eyes glowing like a pair of spotlights.]]
** And to top it all off? [[spoiler: He 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!]]
** Not to mention his "Death Scythe", [[spoiler: 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, [[spoiler: 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.
** It cannot be reiterated enough; this woman was willing to burn down the last chance for several children to get an education simply to force Nagisa into the one option she wanted him to have. She treated Nagisa as a way to live her life through him, having made mistakes in her past. She was willing to destroy several others' chances in life to effectively [[ItsAllAboutMe ''better herself alone'']].
** And let's not forget the face she makes during her rant. It looks something like a Lovecraftian baboon demon.
** To reiterate, the appearance of a murderous hitman made the situation ''less'' scary.
* [[FinalBoss The Final Question]]. It may seem out of line compared to most of these examples, but consider it from the position of a student. It's the end of an incredibly hard series of exams, you're completely exhausted but there's no stopping because you don't know how far everyone else will go, and then this thing shows up. It's a college-level geometry problem, miles above the level of anything that came before, intentionally worded in an extremely confusing way, and it's worth ''a fifth of your grade in that subject''. Is there any worse nightmare for a student? [[spoiler:Fortunately, there's an easy way to intuit the answer, and there's no need to show your work.]]
* The Principal. Asano is not right in how he treats everyone, including his own son, callously and that centipede motif....
** And 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 end the Class E completely, which is 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.
** If you think about it, this is mild compared to what he's done to some other people. Remember that bum a few chapters back? The one Asano gave some money to? [[spoiler: 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.
* Six words: [[spoiler: [[WhamLine "I love you, Koro-sensei. Now die."]]]]
** The scene is so terrifying because [[spoiler:Kayano]] reveals they have a set of black tentacles on the nape of their neck. Not tentacles doubling as hair, like Itona, but black tentacles connected right to the nape of the neck.
* Then, when the first attempt is unsuccessful, [[spoiler: Kayano meets Koro-sensei for what is essentially a SuicideAttack[=/=]SelfDestructiveCharge. But that's not the creepy part. She's sweating so much she looks sick, looks more and more deranged the longer the fight goes on, and is explicitly stated to be losing her mind.]]
* How Koro-sensei got close to the woman in his flashback. [[spoiler: He was captured to be used in an experiment and she was the one who interacted with him personally through a pane of reinforced glass. That's not the scary part: the scary part is that the head doctor, her fiance, knows that if Koro lost control or became too enraged, his new powers would enable him to get through that glass and kill her with ease. The doctor even outright calls her a potential sacrifice!]] She was close to him because the other researchers wanted someone expendable in that position.
* Koro-sensei explains in detail what happened to the moon. [[spoiler: It wasn't him. It was a mouse implanted with his cells that exploded when the mouse reached the end of its life. If Koro-sensei isn't killed, he'll self-destruct and take Earth with him!]]
* [[spoiler: Koro-sensei's transformation is grade-A body horror in chapter 139.]]
* Episode 21 starts out with the mastermind behind poisoning the students [[spoiler:Takaoka]] watching the kids and the teachers on security cameras and saying that once he kills them all and destroys Koro-sensei, maybe he'll use the reward money to buy more kids and ''fill them with the virus and watch them die.'' All this as he's scratching skin off his own face, [[spoiler: which he's been doing since he was removed from the school after being defeated by Nagisa. ]]
** The scratching off his face and the ThousandYardStare doesn't even cover it: Once he forces them all to the roof, he says that his assassination plan would've gone well if Kayano and Nagisa had gone by themselves: First, filling his bathtub with Anti-Sensei [=BBs=] and burying Koro-Sensei and a tied and gagged Kayano in them and covering the whole thing with cement, leaving Sensei to blow up everything if he wanted to get out but knowing Koro-Sensei loves his students, he would choose to die in there with her. As we know, the plan went wrong for two reasons: one, the non-infected kids banded together to save everyone, [[spoiler: and two, Kayano would've melted away when she was placed in the bathtub or would've blown up the entire place to get herself out of there alive. Not that she would've cared about leaving Sensei in there.]]
** [[BewareTheNiceOnes Nagisa]] after [[spoiler: Takaoka blew up the antidote, dooming the students who were infected.]] His eyes were ''[[GlowingEyesOfDoom glowing green]]'', for crying out loud.
* On that matter, Nagisa's snake motif. It shows up several times during the series, when Nagisa uses his [[KillingIntent bloodlust]]: Karasuma senses it during a training exercise before Takaoka shows up, and is scared out of his wits. Takaoka sees it during his [[spoiler:first]] fight with Nagisa, where he [[spoiler:hallucinates a giant snake strangling him as Nagisa makes his attack.]] Karma perceives it in the classroom civil war, where Nagisa appears surrounded by demonic snakes. Perhaps the worst of all is when [[spoiler:Nagisa kisses Kayano to break her free of the tentacles' influence]], where it's portrayed as [[spoiler:a rabbit being ''strangled to death by a giant snake!'']] It's unclear whether this is just an artistic portrayal of the bloodlust, or a hallucination, but either way it's pretty scary.
* The fact that, in a span of a school year, Korosensei raised an [[ChildSoldier entire class of assassins]] [[spoiler:that are just as capable as he is in his prime.]]
* Remember the Fake God of Death? He's back and is now even more powerful than Koro-Sensei!
* There's a scene where Shiro is discussing his latest plan to kill Korosensei, and a mouse from one of his magic tricks crawls up into his mouth. ''And he eats it''. [[spoiler:In light of that, it's probably not too surprising to learn he's resorted to injecting himself with tentacle cells...but it is also very, very bad news.]]

* Remember the Fake God of Death? He's back and is now just as powerful as Koro-Sensei!

* Pitch Black: Furious. Koro-Sensei truly angry is terrifying, in both appearance and intent. In five seconds he gathers the name plates of his students and all of his students friends and family from their houses. He knows where everyone lives. If he wanted, he could kill ''anyone'' but the students. There's nowhere to hide.

* Pitch Black: Furious. Koro-Sensei truly angry is terrifying, in both appearance and intent. In five seconds he gathers the name plates of his students and all of his students friends and family from their houses. He knows where everyone lives. If he wanted, he could kill ''anyone'' but the students. There's no where to hide.

** It cannot be reiterated enough; this woman was willing to burn down a the last chance for several children to get an education simply to force Nagisa into the one option she wanted him to have. She treated Nagisa as a way to live her life through him, having made mistakes in her past. She was willing to destroy several others' chances in life to effectively [[ItsAllAboutMe ''better herself alone'']].

* Episode 21 starts out with the mastermind behind poisoning the students [[spoiler:Takaoka]] watching the kids and the teachers on security cameras and saying that once he kills them all and destroys Koro-sensei, maybe he'll use the reward money to buy more kids and ''fill them with the virus and watch them die.'' All this as he's scratching skin off his own face, [[spoiler: which he's been doing since he was removed from the school after being defeated by Nagisa, leaving ]].

* There's a scene where Shiro is discussing his latest plan to kill Korosensei, and a mouse from one of his magic tricks crawls up into his mouth. ''And he eats it''. [[spoiler:In light of that, it's probably not too surprising to learn he's resorted to injecting himself with tentacle cells...but it is also very, very bad news.]]

* Remember the Fake God of Death? He's back and is now just as powerful as Koro-Sensei!

* The fact that, in a span of a school year, Korosensei raised an [[ChildSoldier entire class of assassins]] [[spoiler:that are just as capable as he is in his prime.]]

* On that matter, Nagisa's snake motif. It shows up several times during the series, when Nagisa uses his [[KillingIntent bloodlust]]: Karasuma senses it during a training exercise before Takaoka shows up, and is scared out of his wits. Takaoka sees it during his [[spoiler:first]] fight with Nagisa, where he [[spoiler:hallucinates a giant snake strangling him as Nagisa makes his attack.]] Karma perceives it in the classroom civil war, where Nagisa appears surrounded by demonic snakes. Perhaps the worst of all is when [[spoiler:Nagisa kisses Kayano to break her free of the tentacles' influence]], where it's portrayed as [[spoiler:a rabbit being ''strangled to death by a giant snake!'']] It's unclear whether this is just an artistic portrayal of the bloodlust, or a hallucination, but either way it's pretty scary.

* On that matter, Nagisa's snake motif. It shows up several times during the series, when Nagisa uses his [[KillingIntent bloodlust]]: Karasuma senses it during a training exercise before Takaoka shows up, and is scared out of his wits. Takaoka sees it during his [[spoiler:first]] fight with Nagisa, where he [[spoiler:hallucinates a giant snake strangling him as Nagisa makes his attack.]] Karma perceives it in the classroom civil war, where Nagisa appears surrounded by demonic snakes. Perhaps the worst of all is then [[spoiler:Nagisa kisses Kayano to break her free of the tentacles' influence]], where it's portrayed as [[spoiler:a rabbit being ''strangled to death by a giant snake!'']] It's unclear whether this is just an artistic portrayal of the bloodlust, or a hallucination, but either way it's pretty scary.

** [[BewareTheNiceOnes Nagisa]] after [[spoiler: Takaoka blew up the antidote, dooming the students who were infected.]] His eyes were ''[[GlowingEyesOfDoom glowing green]]'', for crying out loud.