In the first game, when Ansem, Seeker of Darkness possesses Riku, he speaks with the voices of both himself and Riku. Riku's own voice is dull and flat, and all the inflection comes from his "passenger".
Vanitas does the same with his own voice and Ven's at the end of Aqua's story in Birth by Sleep.
The Japanese version of Axel's kamikaze death was bad enough that it had to be censored for Western audience. To clarify, Axel's element is fire, so he essentially burned himself alive.
Similarly, Axel executing a kneeling Vexen from behind after Vexen begged him to stop in Chain of Memories could be upsetting. The modifications made to that scene in Re:Chain of Memories made it even worse by immolating him on-screen as Sora watched in horror.
Zexion's death, like Vexen's, was made much more horrifying in Re:Chain of Memories. Instead of having the life drained out of him off-screen, Riku-Replica holds him by the collar as he begs for his life, and the camera watches from behind as he stops resisting and his feet are left to dangle lifelessly.
Larxene's death isn't as graphic, but when she realizes she's fading away, she starts desperately grabbing at the pieces of her being, trying to keep them in. It may be worse in the Japanese version because her voice actor sounds absolutely terrified while it's happening.
Not exactly, their bodies still belong to the original Heart. But think about a Nobody reforming into its somebody. Its said outright that a Nobody has a separate sense of self and personality inherited from the Body and separate from the Heart. Now, when they reform, said sense of self is assimillated back into the original Heart. That wouldn't be a problem if the Nobody adopts a persona like the original (ie. Axel), but what about for those who didn't? Fading into the darkness waiting for your Heart to be liberated is already bad enough, imagine your sense of self and your indviduality being stripped away forcibly. Yikes.
Neoshadows, more poweful version of Shadows, made their debut in - Sequel Hook trailers aside - the Japan-only updated re-release of the first KH game. While their Chain Of Memories and Kingdom Hearts II counterparts behave like regular enemies, their original self are more cunning, as they actually plan during battle. One of their most unsettling tactics involves a Neoshadow pinning Sora down while the others do the rest.
Some of the little details in the way dying or pained characters are animated are pretty upsetting upon closer inspection. Among the worst include Roxas involuntarily twitching as Ansem-Riku choked him into unconsciousness, Zexion's feet swaying around like a hanged man's as the life was drained out of him, Riku-Replica looking very much like a corpse when his heart was broken, and Master Eraqus falling forward towards the camera with unblinking eyes when he was killed in Birth By Sleep.
There's a section in the End of the World called the World Terminus. You go through, fighting through small sections of the other worlds in the game, all familar areas (The Third District, Rabbit Hole, Agrabah etc). Then you come to Hollow Bastion, and access what is implied to be the freak-lab where most of the Original Generation villains' Start of Darkness happened. Just for context, here's a Let's Play showing said lab.
Other frightening locations include The Heartless Manufactory and the secret basement laboratory operated by Xehanort and his fellow apprentices. The Manufactory is a location in Kingdom Hearts II where the MCP starts mass producing Heartless in order to invade Radiant Garden, and is also, according to KH 3 D the place some of the original members of the Organization lost their hearts. The basement laboratory contains a prison-like area in which the doors are chained shut, which is implied to be where Xehanort's human test subjects were held, as well as the Chamber of Repose, in which Aqua's armor is placed. Xemnas is not to be disturbed while he is down there, under any circumstances.
While this is only thinly connected to the games and is VERY cartoony, the manga has its moments, one in particular had a huge case of Mood Whiplash . You know how when Shan-Yu gets defeated in Kingdom Hearts Two he just passes out? That's not it plays in the manga. Once Sora defeated Shan-Yu, he is one the ground and is approached by Xigbar. Shan-Yu begs for more power, what does Xigbar do? He shootshim. The manga is rated E.
Most of the chapter has normally happy-go-lucky Sora being pushed beyond his limits. He looks absolutely pissed that Shan Yu, The Heartless and Xigbar are keeping him from finding Riku. Well, at least until the above happens.
Many of The Disney Villains can still be Nightmare Fuel when you fight against them, like Giant Ursula, Maleficent in her Dragon form and others. Just cause you've gotten older doesn't mean they still can't scare you like they did when you were a kid!
In Hollow Bastion, the Disney Princesses were imprisoned in the People Jars intended to essentially suck their life force out. They're implied to have been in there for years, aside from Jasmine, Alice, and Snow White.
After his friends vanish, Winnie The Pooh starts wondering how he can "say goodbye to Pooh" when he disappears too. It comes off as a metaphor for death, which is rather disturbing given the source.
The manga has another interpretation of this scene. A Soldier Heartless rips out the heart from a woman (who's implied to be a whore) while she's flirting with Sora. Then the Soldier crushes the heart within his claws.
On the night Destiny Islandis destroyed, Sora sneaks outside only to find a storm, invulnerable Heartless devouring the whole world and Riku being swallowed by darkness. Even after he obtains a Keyblade capable of destroying the Heartless and defeats the giant being of darkness that towers over his islands, he's blown away as the world gets destroyed.
Kairi's Dull Eyes of Unhappiness coupled with Creepy Monotone when she appears in this sequence makes it feel even more like some kind of nightmare. All she can say is "Sora..." before wind blows her away like a ghost, she fades through Sora, and disappears.
The final boss itself can be best described as some kind of organic ship, connected to a giant-sized version of Ansem by thick, fleshy cords that may or may not be its entrails. Despite Ansem controlling it, said ship also sports a Nightmare Face of its own.
Pinocchio's world in the first KH game is represented as Monstro. The inside of the whale is basically a Womb Level, and everytime it's accessed, the Gummiship doesn't land. It gets eaten whole.
Dying in the original "Kingdom Hearts" can be rather startling. When the HP bar reaches zero, several things happen in rapid succession — Sora groans, the camera zooms in and circles around him, the screen fades to white, and the Game Over screen appears. In future games, it's slowed down, which makes it come as less of a shock.
In the G.O. screen itself, Sora is dead, floating limp in complete darkness, with his heart floating outside of him.
When the shark from The Little Mermaid appears out of nowhere in the haunted ship in Atlantica, it can be quite startling.
The battle against Chernabog is equal parts Nightmare Fuel and Crowning Music of Awesome. To clarify, the guy is the Slavic equivalent to Satan — he's a giant black demon, whose face is bigger than Sora is tall, and he's known as one of the most terrifying beings in the Disney canon.
And the best part? There's no warning he's even in the game. If you're playing it for the first time you don't even suspect him showing up this late in the story if at all. But no, he shows up as pretty much the penultimate boss of the game.
In Neverland, while traversing through Hook's ship, Sora is attacked by multiple doppelganger Heartless known as Shadow Sora - jet-black, no weapons, flies through the air, dances until it deems you worthy of receiving of an attack. When you defeat it, the experience point display reads Tech150p. "Tech" points are normally rewarded when Sora parries an enemy strike. Then it hits you: Riku isn't just sending out clones of Sora; he's actively attacking him.
The intro to the game itself is disturbing enough to keep you from playing through it AT ALL. From the unreal music to the all-consuming darkness surrounding your stained-glass prison of a tutorial space. The silence and lack of a voice or many other sound effects in the first stages doesn't help either. This all culminates with a massive shadow monster that you're expected to defeat, alone.
I can't be the only one who just remembered that basically in the end of the game Riku and Mickey Mouse are stuck in the Disney version of hell.
Kingdom Hearts: Chain of Memories
Sora slowly losing all of his memories in CoM, specifically replacing Kairi — one of his best friends — with NaminÚ, was rather disturbing. The depth of his brainwashing was made most explicit when Sora begged NaminÚ to break his heart to save herself, knowing that she'd been manipulating him the entire time and that he'd probably end up catatonic, staring at nothing just like the Riku-Replica.
NaminÚ is deathly afraid of her captors, Marluxia and Larxene. Larxene is known to revel in cruelty, and Namine's reaction suggests that it may not all have been shown on-screen. Even more disturbing is her obvious terror whenever Marluxia is around. The way she jerks away when Marluxia touches her on the shoulder just makes it worse.
Vexen's death in the manga. We're treated to a glorious two-page spread... of Axel punching a hole through Vexen's chest.
Kingdom Hearts II
The Dusk Nobodies move with a strange boneless gait and tend to resemble humanoids made of cast-off gray and white clothing. Organization XIII is made of the same Nobodies, just humanoid in form.
Axel lampshades this early on, near the end of Twilight Town.
Axel: "Man, oh man, even the Dusks aren't gonna crack this one."
The Dusks are extremely weak enemies, so he almost certainly isn't referring to them in their capacity as combatants.
Also potentially frightening is the fact that Organization members are constantly threatened with being turned into one of the aforementioned Dusks as a punishment.
It was easy to get Mood Whiplash when entering "The World That Never Was" at the end of the game. It gives off this bizarre feeling of family-friendly existentialism, with creepy background music and floors with names like "The Altar of Naught", "The Hall of Empty Melodies", and especially "Proof of Existence" — the Nobodies aren't supposed to exist, and they believe their death means absolute Cessation of Existence, so that graveyard-like room is the only proof they ever existed.
The game started with Roxas essentially losing his own individuality, forced to re-join Sora in spite of his desire to be his own person.
Sa´x, during his boss battle, tends to yell "All shall be lost to you!" with the voice of a complete psychopath. The guy's pretty much The Berserker, mostly due to his moon-based powers inflicting him with literal lunacy.
Actually it's not completely random. Each form (besides Final, which acts as a Nobody analogue instead), when used, adds a certain number of points to an unseen counter. The chance you'll enter Antiform increases after the points exceed certain amounts, and Final form gives a large reduction to these points. Knowing this mitigates the nightmare potential somewhat.
Right after Sora and Riku are left stranded in The World That Never Was, the entire world they are in begins essentially caving in on itself.
The final part of the final battle takes place literally nowhere, in a place that doesn't exist. Go with it.
Of course when Sora and Riku return to The World That Never Was it's practically undamaged which means that the world that was caving in on itself that Riku and Sora were stranded in at the end of KH2 was actually the Kingdom Hearts that the Organization created and it wasn't caving into itself. It was being absorbed by Xemnas using The World of Nothingness ship which is hinted in the game files to be the outside of the strange world of nothing where the final part of the final battle takes place in.
The battle against Twilight Thorn at the beginning of Kingdom Hearts II. That boss is the Nobody counterpart of Darkside, and holds Roxas captive at any given possibility.
Oogie-Boogie's first demise is just like in the movie — his burlap skin unravels, and zillions and zillions of bugs start crawling out all over the place. The whole "bugs-in-Oogie's-shape" part, however, is thankfully scrapped.
Xemnas's OHKO attack in Kingdom Hearts II: he's trying to forcibly tear away Sora's heart.
In the manga, seeing Radiant Garden Tron being tortured by Sark is horrifying enough on it's own, but considering what happens to the real Tron, especially after Sora defeats him in KH3D...
Regardless, seeing any characternote that does not deserve it getting tortured by electrocution is horrifying. The main trio even go through with it, with the torture victims being Donald and Goofy in the game, and Sora in the manga.
Xion's comments during battle imply that she wants Roxas to defeat her. It's implied that she is still in there, and wants Roxas to kill her so she won't have to destroy him.
The secret reports reveal that she was feigning her insanity. Doesn't make it less scary, though
Right before said battle, Roxas goes up to the Clock Tower to angst, when Xion joins him. For some reason or another, she has her hood up. After a rather cryptic monologue, she takes off the hood... cut to Roxas, with a look of shock on his face. Xion continues talking, as we pan up to her face... and she looks just like Sora now, except for the voice. Then she steps off the clock tower into thin air, and turns around, hood up again, with only her eyes visible. Light starts flashing around her and she says, in Creepy Monotone, "You're next, Roxas. I have to make you a part of me too." Then the fight starts.
"Snarl of Memories" is perhaps one of the most infamous mind screws in the entire franchise, which is saying something. There are no proper ways to describe the cutscene without it being Natter Bait, so this link will speak for itself.
"IT'S THERE... IT'S HUNGRY... DON'T TURN AROUND!!" is an inscription in one of the Twilight Town tunnels in Kingdom Hearts Days. It actually had nothing to do with the mission — it was randomly thrown in just for the sake of screwing with the players.
Not exactly, the sign could be referring to the first powerful Heartless you fight down there, or the heartless in general, it is nontheless unnerving.
In the first trailer for Birth by Sleep, Ventus' No-Holds-Barred Beatdown at the hands of Master Xehanort ended with the former being frozen alive and aware of it. Then he falls off a cliff, parts of his Keyblade and armor shattering as he collides with the cliff's face. If Aqua didn't catch him, he could have shattered like glass.
It's worse when this happens in the actual game, since you get to see the aftermath. Being frozen sounds quite painful.
Vanitas is both sadistic and insane at the same time. The fact he looks and sounds exactly like Sora if he had black hair and yellow eyes makes it a thousand times worse.
The fate of Cinderella's stepmother and stepsisters harkens back to fairytales of old as their crimes are punishable by fiery death at the hands of the Unversed. The camera cuts away before we see anything, but judging by the look on Cinderella's face, the result wasn't pretty.
The Unversed, while not as disturbing as the Nobodies, have the colorful appearances of the Heartless, but none of their cute aspects. Several Unversed take on the appearances of harmless items (like a pumpkin) apart from their creepy features and powers. Their only consistent features are their red eyes, dagger like appendages, and the Unversed symbol.
The tornadoes chasing players down don't help matters. They're massive, difficult to avoid, and each one of them leads to a battle in a freaky alternate dimension with some of the most powerful standard enemies in the game.
The ruins of the Land Of Departure are quite creepy, especially if you run into them in Ven or Aqua's story first and have no idea how it got that way.
The secret ending of Birth by Sleep Final Mix. After an entire secret episode spent in isolation in the Realm of Darkness fighting Heartless, Aqua runs into something rather startling — the Castle of Dreams, corrupted by the darkness and surrounded by evil-looking clouds. It doesn't help that a somewhat distorted version of Destati starts up at that exact moment.
The Hunter of the Dark boss from the secret episode is fought in total darkness. It stalks Aqua from the darkness when it appears, only its red eyes visible, before the camera shifts to its perspective as it attempts to pounce.
The cutscene before the battle starts from the boss's perspective. You then see the red light from its eyes appear and zip across the clearing. When the eyes first appear, it looks like they're looking at you, not Aqua.
When you defeat Master Xehanort in Terra's penultimate boss battle, you can hear him say, in a faint yet distinctly chilling tone, "Only now... have I truly won...". Considering how emotionally charged the cutscene before the fight was (featuring probably the most believable voice acting Jason Dohring does as Terra), the feeling of triumph is quickly dashed by that one short line and what comes after it.
Aqua being strangled in the final story. Not only is it unnerving to see one of the main characters have this happen to them; another level of horror is added when one realizes that it is essentially Terra doing this to her.
Heartless aren't as widespread in this game as they are later. People losing hearts isn't that much of a problem. Then, when you first get a game over, it hits you, unlike the standard lifeless body with floating heart implying you became a heartless of later games, there's just a lifeless body. That's right, you're not facing being turned into The Heartless with a chance, however slim, of coming back, you outright die.
Kingdom Hearts: coded
Sora's Heartless is somewhat disturbing, considering how nice Sora himself is.
The data version of Castle Oblivion is in some ways even more disconcerting than it was in its original form, because the illusions don't actually work on Data-Sora
In Agrabah, Jafar gets a hold of a glitch-created copy of Genie's lamp, and promptly uses it to freeze time. Data-Sora then has to race against time in a monochrome-green, almost completely silent Agrabah.
Kingdom Hearts: Dream Drop Distance
Judging by the Dream Drop Distance trailers, Ienzo turning into his nobody form was forced upon by Terra-Xehanort.
Master Xehanort's latest plan combines Ven's fate and Terra's. In short, not only is Sora comatose from his Heart being broken, but Xehanort wants to turn him into Soranort. And even after Mickey and Riku rescue Sora from Xehanort, he's left comatose, in the same position (metaphorically and literally) as Ven. Knowing he gets better doesn't really help.
The deliberate amount of Mind Rape that Xehanort put Sora through in order to render him comatose actually outright tops what he did to Ven and Terra, because it's not just in The World That Never Was that he does it in, no that's just where he goes all out, he does it in every single world he meets Sora in. No attempts to be a decent guy, nothing, he just gets right to business this time around.
Does anyone else find the concept of 13 Xehanorts running around at the same time horrifying?
Not just the concept of 13 Xehanorts, but the fact that out of the six we already know about, two of them were achieved by Xehanort possessing someone other than Terra... Braig and Isa. When you think about how different Isa in Birth by Sleep was from Saix, and consider that Saix has had the yellow eyes and pointed ears associated with Xehanort possession ever since his first chronological appearance in Days... he's been possessed for at least a year, and we have no idea how aware of it he was.
Dream Drop Distance also demonstrates that, despite being an old man, Master Xehanort can still be pretty damn scary while doing nothing but talking. The way he casually talks about how badly he screwed up the lives of Terra, Ven, and Aqua while slouching in his chair and smirking really shows how far he's jumped off the slippery slope. Props to Leonard Nimoy for doing a truly chilling job.
One of the truly scary parts of DDD was one scene with Yen Sid. After learning the true extent of Xehanort's planning extending to putting his Heartless in Destiny Islands at the point of its destruction solely to make sure he can time travel there, he promptly freaks out, and the realization comes across that for all of his calm planning and advice, Master Yen Sid is terrified. OOC Is Serious Business was heavily in effect. It calms down quickly, but it also puts into perspective the scene with Kairi in the secret ending as a last ditch effort to throw a Spanner in the Works, rather than just trying to protect the Princessses.
Not to mention Rinzler's very existence (or lack thereof). Even if he isn't the TRON Sora knew (the Tron from the Grid and the original ENCOM server and the Tron from Space Paranoids are two different characters) you still feel for the poor guy.
Sora's dream version of The World That Never Was. The place is a twisted wreck, with buildings sliced in half, others contorting crazily, and 'Contorted City' has large chunks of building flying at you. What's really the icing on the cake though is the world theme ("Sacred Distance") that sounds like a distorted and unsettling version of "Dearly Beloved".
Anti Black Coat Nightmare. Despite the Word Salad Title, he is extremely scary in his own twisted way. He has attacks that look similar to a fountain of blood, and is extremely fast. Even though his attack that sucks out almost all your health can be blocked, you may not see it coming.
The existence of The World Ends with You characters in Traverse Town, with the exception of Joshua. First, in order to be caught in the Reaper's Game that they seem to be caught in, they needed to die in Shibuya. Then, while they were dead, before they could win their game and come Back from the Dead, Shibuya is destroyed by the Heartless, resulting in all of their destruction. Joshua, consciously aware of this due to being the Composer, cannot save their souls, instead fashioning Living Memory copies of them out of Rhyme's dreams. They continually play the Reaper's Game, but the problem is that there are no Reapers in Traverse Town as far as anyone can tell. There isn't truly a Game at all anymore, and it is just their lives ticking away. And if Joshua does return to Shibuya somehow and reunite with their spirits, who's to say that the entire reason for the Game won't be brought into the picture? And that's not even bringing the entry fee issue up.