—Ragna, during his encounter with Arakune in Calamity Trigger Reloaded
Ragna wasn't kidding. While BlazBlue isn't the Trope Namer, that doesn't stop it from having a disproportionate number of scary moments.
WARNING: Spoilers ahead.
From Calamity Trigger, Ragna and Nu fusing together and forming the Black Beast. Her childish giggling does not help at all.
Nu-13 is usually a stoic Robot Girl, always speaking in a robotic monotone, finishing her tasks with surgical precision... unless Ragna is around. She then regresses to the personality of a young girl, and turns her Yandere index up to19. It's absolutely mortifying.
We finally get to see exactly how Ragna lost his arm, and it is not pretty. Seeing a young Ragna, his arm cut off, surrounded by a ring of fire as a Yukianesa-possessed Jin looms over him, all while Terumi's silhouette watches with twisted amusement is beyond freaky. Picture here◊.
In Carl's Bad Ending, he confronts Hazama, who beats him and props Carl up where he is helpless, then begins slowly tearing Nirvana apart. Carl desperately pleads for him to stop, but he continues and breaks her into pieces. Hazama then grabs Carl by the collar, sickly grinning and delivering a brutal Breaking Speech to him, before finally throwing him against a wall and killing him. The whole scene is both awesome and terrifying. Picture here◊.
Ragna's Bad Ending is a definite example. Ragna's Azure backfires from overuse and turns him into a new Black Beast. He can do nothing as he ravages across what's left of the world and destroys it. The chilling screams of the people he devours do not help.
A bit more detail... Arakune Was Once a Man, but after trying to tap into the power of the Boundary and experimenting on his own body, he began to degenerate. Now he's nothing more than a black mound of goo, smelling of trash, filled with bones and disgusting insects, and eating anyone he comes across. His speech is fragmented, and he swings between insane laughter, paranoid rambling, nihilistic threats and tortured screams. As of Continuum Shift, he seems to be regaining his sanity in short bursts, mostly warning Litchi to stay away from the Boundary. And even at his craziest, he's aware that the is SOMETHING wrong with him, but he can't quite place it.
Just when you thought it couldn't get worse, it did. If you were too distracted by Arakune's Creepy Awesome factor, or his Woobie points above and possibilities that he's learned his lessons once Litchi probably cures him, Chrono Phantasma finally turns him into the terrifying monster he's supposed to be with his new Astral animation. Remember how nothing happened when he hit the opponent? Now something does happen, and that something is very, very grotesque even for BlazBlue standards: the opponent gets sucked into (read: devoured by) Arakune and is trapped in a giant spider web. Then all of a sudden a bunch of HUGE eyeballs pop in from the background as a swarm of spiders, with the exact same eyes on their backs, begin to crawl out of the huge eyeballs and close in on the opponent, covering the screen in the process. Once the screen is completely covered by spiders, you hear a very loud and unnerving "CRUNCH!" as the Astral Finish display pops up. Once the screen clears, nothing is left. Yes, you know what just happened. That poor soul just got eaten alive by spiders. And now their blood is raining down on the screen.Holy. Fucking. Shit. Prime phobia trigger for Noel.
Terumi: "Ouroboros!! Picked a great time to grow a pair, huh? YOU'RE gonna play with ME? I don't think you understand how this shit works!"
Makoto's bad ending is royally messed up. Relius Clover captures her and subjects her to mental torture, to the point where she is crying out for him to stop. By the time he's finished, her soul has been completely and utterly shattered, leaving her with no willpower to do anything anymore.
There's a particularly chilling portion of this ending where all we hear is Makoto sobbing, pleading with Relius to stop, and a few times mentions what he's doing is hurting her, while he ignores this and says he will go on. What makes that even worse is that their character portraits aren't shown at this time, amplifying the effect of us hearing a rape in progress.
You may ask yourself, "Is there any way this ending can get worse?" Watch it with the Japanese voices on. See that Big "NO!" Makoto gives in the dialogue above? In the Japanese version, she screams bloody murder.
Even the Help Me Professor Kokonoe segment is chilling due to Makoto still begging for mercy even after she's entered Kokonoe's lab.
Relius: You've just given me the fulcrum I need to topple your soul, and reshape it however I choose...
Want more? Use his Astral Heat (Puppeteer's Altar). The opponent is trapped in one of Relius' labs and restrained in some way. If you'll notice, the walls are smeared with the blood of past subjects, who are hanging above on swinging crosses, the shadows of which can be seen. Relius then nonchalantly alludes to what he's going to do to him/her and the doors slam. All you can hear over the announcer is the death cry of the victim. For even more horror, some of the "experiments" are particularly gruesome. While Hazama is dying of boredom ("Not like I don't deserve a hundred times worse...") and Tsubaki's appears humane (despite her facing the wrong way due to blindness, and more about Relius being savvy enough that Tsubaki's utter loyalty assures that she's not going to rebel), it is heavily implied that some characters are brutally killed or abused. Noel is trapped, naked, in a large structure, with a spike positioned in between her legs pointing directly up at her crotch. Platinum is trapped in a barrel with holes in it, after which numerous swords skewer her through those holes. Yeah, he's that kinda person.
His Astral Finish on Rachel isn't especially gruesome, but is rather tragic if you think about it. Nago and Gii, despite the abuse she heaps on them, are clearly very loyal to Rachel. During the Astral Finish, the two (or at least Nago) are forced to keep her bound so Relius can do whatever he want's to her.
Some say that nightmares can begin with a sense of safeness. In that very case, the combination of Litchi and Arakune's Bad Ends count. We were lured into a sense of happiness and heartwarming that we saw Arakune still has enough heart and care about Litchi's welfare, trying his best to remove her from his curse, and she is able to live on her life normally without any memory of him... in which we later learn that the corruption within Litchi is similar to Alzheimer's disease. Without a cure, it will continue to rot her until she dies, and all Arakune took was memories of him, and without his memory, Litchi becomes unmotivated to find the cure and blissfully unaware of it, awaiting the day she withers and die with her memories being jumbled here and there, or at worst, become the next Arakune and then start eating everyone nearby until someone kills her. Now then, when your choices are keep making bad decisions of continually working for Obviously Evil guys to pursue the cure as it's the only way or forget the cure and then get inflicted with this... Her desperation and 'obsession' would look justified, you don't want to get into her situation! At least those bad decisions still let you be in full control, not show that you actually like working for that bastard and show remorse sooner or later...
Carl's entire story. Even if he does become a adult, even if everything is okay for Carl, the kid's gone through enough crap to rival Ragna. He dropped out of the Academy after his father integrated his sister into Deus Machina: Nirvanaand left her half-done for the boy to finish, and was effectively abandoned to grow up on his own terms making a living as a vigilante. On top of that trauma, it is implied that Nirvana amplifies the bloodlust of its wielder and stymies other emotions to that end, leaving him cold and emotionless on missions and a broken wreck that distrusts the adults around him otherwise. While Bang and Litchi did comfort him to a degree, he nearly broke all over again when he realized that Relius' improved detonator doll was built using his mother's soul. The kid's about as stable as Shinji, and who can blame him?
Mind Eater is a form of geas that, while it allows the subject to somewhat freely express themselves, any command that is issued by the controller will be executed whether the subject wishes to cooperate or not. After overtaking Kazuma and slaying Tomonori (the latter is somewhat justified, as Tomonori was trying to kill Kazuma to prevent the merge) alongside his role in the Black Beast's creation, Terumi deserved no less... not that he took his rehabilitation very well, mind you.
Nine knew a more advanced form, called Ruby: Mind Eater, that further overwrites the subject's will, reducing them into a warped puppet of the controller. This technique was used on Tsubaki, and had she not been saved by Jin, Noel, and Makoto, her mind would have been totally consumed until she became the Imperator.
In a nutshell, anything and everything involving Yuuki Terumi!
But let's go into specifics, shall we? To kick things off, Terumi's default theme is always Endless Despair, so you know right away he's not fucking around. Then the fighting starts. His pure sadism, incredibly painful looking moves and distortions, and his incredibly joyous laughter as he's ruthlessly beating down his opponent is a terrifying sight to behold. Even it is meant for comedy, this video shows off just how insanely sadistic the motherfucker is.
Azrael is walking, talking Nightmare Fuel. The fact that Hakumen, the very same Hakumen who can cut through time itself and is the de facto leader of a group of six beings considered to be the strongest warriors on the planet, flees from him rather than fight him should tell you everything you need to know about him. And don't get started on what he's like when he really starts getting worked up and into a fight.
Trinity's Plan. Simply put, She needs Bang to activate the Lynchpin, wiping off all sether from the planet. Think a little closer, and it's nothing more than a Kill Them All to kaka kind (As well as Ada and Ignis), and a major loss of civilization's power source, all just to cripple Terumi and his operations
The Doomsday itself. With Relius having stripped the limiters from every cauldron in the world, the seithr is overflowing and overdosing everyone from the top of the hierarchical cities downward, with all the terminally corrupted disintegrating where they stand. Imagine seeing black smoke spew forth from a volcano, but everyone it washes over just disappears before your very eyes, and you have a good idea how horrifying it would be. And then there's the sea of seithr in the lower elevations, so given long enough there would be nowhere left to hide. This is such a nighmarish scenario that the aformentioned plan to activate the Lynchpin is preferable to allowing this to continue!