[[quoteright:259:https://static.tvtropes.org/pmwiki/pub/images/images_1_56.jpg]]
[[caption-width-right:259:[[NightmareFace Yikes...]]]]

* Comes in high doses in Season 3. Quick rundown:
** Enzo, [=AndrAIa=] and Friskett playing a ''Franchise/MortalKombat'' spoof, complete with an unbeatable User who slashes out Enzo's eye. In order to escape nullification (which is a ''major'' NightmareFuel concept in its own right) they have to enter [=GameSprite=] mode and leave Mainframe with the Game, leaving Dot to think that her only family was nullified. Oh, and Enzo and [=AndrAIa=]? They're KIDS.
*** The user's character fights a number of fighters and every time applies a finishing move of gripping a clawed hand around a victim's head, and then some crunchy [[SoundOnlyDeath Sound-Only Violence]] occurs and a ominous sting plays. Keep in mind that the most memorable thing of Mortal Kombat to many people was the icky fatalities, and Sub-Zero's ripping out the head and spinal column was widely considered the ickiest. This was all but stated as an obvious homage, and innocent young Enzo is watching all these other CPU characters go through something too violent to show on-camera. He's actually somewhat mature about it, but then he's last seen laying defeated with the hand coming down over his face. And then the sting plays, as the camera cuts to [=AndrAIa=] and Frisket stuck spectating. Now that's cold.
** The lead ups to the kills are pretty bad, as we see we see the neck muscles of the characters begin to stretch [[GoryDiscretionShot before we cut away]], along with [=AndrAIa's=] horrified reaction. When Angel is killed, we're treated to a shot of Angel's (an AI fighter) feathers floating around and the User's fist closing, red with what only could be blood.
*** Dot is anxiously waiting outside waiting for the announcement that Enzo has won the game, with no way to see into it. And then the announcement declares the User to be the winner. Dot is left in the belief that she's just lost the only family she had left via her little brother being nullified.
*** And this is overlaid with Megabyte's maniacal laughter.
** Early in the season, Megabyte makes it very clear to new Guardian Enzo that he views him as nothing more than a messenger boy for Dot, and its the only reason he hasn't murdered him on the spot.
-->'''Megabyte:''' You are what you've always been: a mere delivery boy--do not provoke me further; it is by my will alone you survive this encounter. Be well advised to ''remember that''.
** Enzo and [=AndrAIa=] are stuck in a never ending cycle of violence as they travel from system to system via the games.
** When they finally ''do'' return to Mainframe they find that Megabyte was able to take over and absolutely devastated the system.
** Phong is decapitated by Megabyte and his head is tortured into giving up the passcode needed for Megabyte to infect the supercomputer.
** The first version of the Season 3 opening narration is delivered by Megabyte, declaring "Megaframe" his domain.
* Before all that, there's the climax of "Painted Windows", in which Bob rips Hexadecimal's mask off in a desperate attempt to distract her, and she struggles to [[PowerIncontinence contain her full power]] while Hex's mask comes to life and [[NiceJobBreakingItHero mocks Bob for dooming Hexadecimal to self-destruct by removing her]] PowerLimiter.
-->'''Mask:''' ''Guardian... Guardian! You have removed the only thing that keeps her power in check! Without the mask, Hexadecimal will overload, and '''be destroyed'''! {{You fool}}, you silly fool! [[PrecisionFStrike Damn you!]]''
** There's no face under Hex's mask, just a void that pure energy shoots out of while she screams in absolute pain and terror.
** [[OhCrap And right as Bob is about to undo his mistake, Dot breaks the link to the paint program.]]
** The very end of this episode is a JumpScare where Hex's ThousandYardStare face briefly flashes into her SlasherSmile. Then the screen fades to black but her GlowingEyesOfDoom remain like two green dots on a black background.
** Enzo falling off of the rotating cards and into the many screens can be very frightening to a small child.
** Lost Angles in the episode is especially creepy, being full of abstract art (including nulls with Bob's face on them and imagery based on the works of Salvador Dali)
** Before trapping him as a texture in Mainframe's sky, Hex removes Phong's head and replaces it with a giant apple. For a brief moment he's trying desperately to pull the apple off while letting out muffled screams.
** Several sectors are absolutely flooded with paint, and Megabyte gets his mouth glued shut as Hex turns him into a clown and traps him as a sky texture with Phong.
* Megabyte, infected by the web creature. Black with silver highlights, the claws on his hands permanently extended, [[RedEyesTakeWarning red eyes]], and a serpent tongue.
** There's also Hex's infected form, which involves much of the same, a black outfit with silver highlights, the serpent tongue, blue eyes that turn red as she approaches Mike and Scuzzy, presumably to kill them, and this is not only after we witness Hex being horrified as the web creature held her down and approached her, AND this is also not long after "Painted Windows" (only two episodes removed from it).
* Basically, Hex could always be counted on for SOME form of Nightmare Fuel, intentional on her part or not.
* The very first episode had a creepy scene of Megabyte running up a vertical wall on all-fours, like some kind of HellHound.
** It happens again in the episode where Enzo and Frisket are stuck in the Tor. Also, Megabyte grabs one of his tanks with Enzo inside of it and begins beating it around the room. Anytime Megabyte decides to dish out a physical beatdown (including his climactic battles with the heroes) is some of the show's most violent physical stuff. It only serves to make it scarier when you realize that Megabyte by himself is no match for Hexadecimal.
* The Funhouse, from the game itself to the BadFuture shown as a result of Bob and Dot losing it in "Identity Crisis".
** Why is The Funhouse so feared by Bob when he warns Enzo about it early on in the episode? It's a game of random chance, making it far too easy for the User to win without a large amount of luck on the sprites' side.
** Bob picks the wrong door and gets separated from Dot when the game strings him up like a puppet and forces him to cartoonishly walk into a black void.
** Bob's fate in the Bad Future: a Null living in a cage owned by a homeless Phong who's sadly lost his sanity.
** Dot having hallucinations of the bad future before she actually ends up there.
** Megabyte's public announcement that he's obtained all of the sector's PID codes that Dot had been trying to keep safe, while claiming that Dot herself personally supplied them.
** The bad future, Megaframe. A viral totalitarian state where everyone has a barcode on their forehead and Megabyte rules with an iron fist.
** Oh, and bad future!Enzo has a scar over his eye, just like the one the real Enzo receives in "Game Over." One whopper of a foreshadow there.
* The Web Creature. It doesn't help that its full debut comes in the [[ParanoiaFuel Paranoia Fueled episode]] [[Series/TheXFiles "Trust No One"]] and that the damn thing looks like the unholy product of Cthulu and a vampire. Add in the fact that it drains the life from its victims with highly-visible "veins" that [[{{Squick}} stick out of their skin]] and are organic enough to twitch and writhe in pain when severed... brrrrrr.
* Dot's partial erasure from a magnet. She flashes like an X-ray skeleton, but with huge eyes. Overall it looks very creepy.
* Daemon's infected all come off as very disturbing cult followers blindly following her word. It's a very chilling experience trying to talk to one of them.
* Let's take a look at the before-mentioned Nulls. When a Sprite or Binome is severely damaged in some way or another (losing a game is the most common), they're nullified. All that's left of their data is a little multi-colored slug that gives off [[HellIsThatNoise horrible screeching]] and mindlessly feeds on any available energy. More than once it's brought up that a character's loved one is now a Null, and that's just horrifying.
** Games aren't the only way this happens, as the destruction of Mainframe's Twin City resulted in the nullification of most of the sprites in the system (which is why Enzo has no friends his own age). This included Dot and Enzo's father. And if they hadn't been delayed by the construction of Dot's Diner, it would have included them as well.
* From the video game: Hex's [[spoiler: Dot impersonation.]] She ''looks'' like [[spoiler: Dot]], but moves like Hex, with the sashaying hips. It's ever so subtly ''wrong'' looking and cements Hex as a {{Yandere}}. And then there's the horrible squelching sound when Bob figures it out and pulls her mask off...
** Oh, and how bout her reaction when her plan is foiled, complete with her notorious SlasherSmile mask.
--->'''Hex:''' If you can't love them... DELETE THEM!!
** Many of the GameOver scenes count as well, ranging from Hex ''' '' stuffing '' ''' Bob and Dot's corpses, Enzo's frontal chip being forcefully removed as he becomes Megabyte's minion, and the entirety of Mainframe being destroyed.
* Megabyte steals a box from Hex. Megabyte opens the box. It's a powerful bug that turns everything and everyone to stone, spreading over the city in a wave, and there's no way to stop it. Oh, and everything that gets transformed will eventually disintegrate. Note Hex had the box protected just to lure in Megabyte to steal the box all so he could open it and release the virus ForTheLulz and to just screw over her brother.
** The only way the Medusa Bug gets stopped? Hex herself stops it after Bob points out that a world where everything is frozen in stone is not going to satisfy Hex's lust for chaos.
* The GiantSpider in ''Wizards, Warriors and a Word from Our Sponsor''. Hope you're not arachnophobic kids.
* Matrix's mental state. The time spent in the games, as well as the wars against the web, Megabyte, and Daemon, have left him in a place where, when he's infected by Daemon, it's probably the most at peace he is in the whole series. And the only way to break free is for him to embrace that darkness and hate. It's telling that the first thing we see him doing in "My Two Bobs," the first time since probably NULLZILLA that he hasn't had the active threat of impending deletion or finding a way to survive the games hanging over his head, is a war game exercise in Lost Angles - a war game exercise that, as far as anyone in Mainframe knows, isn't even necessary, because all the viral threats to the system have been dealt with. To say nothing of how HE feels about Little Enzo running around, when "Number 7" established that he hates that older version of himself because he couldn't survive.
* Hex's collaring by Megabyte in the first arc of Season 3 is disturbing in its own right (particularly when you acknowledge that Megabyte also basically put her in fetish gear). As Enzo puts it, "You did that to your own sister?!" (Not helping matters is Megabyte's bemused chuckle and attitude that indicates that he thinks of her almost as his masterpiece in that moment. But then Herr Doktor drops the bigger bomb of an idea: Hex, with her power, may only be PRETENDING to go along with Megabyte's control, even possibly enjoying the shock collar.
** And then, of course, when Matrix and Bob return to Mainframe at the end of the season, we get to see exactly what happens when Hex STOPS enjoying things - namely, she blasts her way out of the Silicon Tor, rips the collar off, blasts Megabyte's forces apart (including Hack and Slash, not like [[RunningGag that's the first time it's happened]], but, in this instance, they're shattered to smithereens, rather than the more typical pile of pieces), and summons a horde of nulls to swarm over a crashed tank, in a way akin to a feeding frenzy.
*** Worth pointing out? Hex has always been capable of this. But she'd never been pushed to wanting to casually ''destroy'' things. Cause chaos, certainly. But outright destruction? That's normally not her style - and all of Mainframe should be GLAD about it.
* Gigabyte. You see everything on this list about Megabyte or Hex and the multiple times pointing out how their character flaws (specifically Hex's insanity and Megabyte's Ego) keeps it in check? Gigabyte has all of Megabyte's intelligence and Hex's power, but with ''none'' of their eccentricities. He is laser-focused on his goal, and up until having a tear dropped on him nothing could so much as even slow him ''down'' (much of the episode is trying to distract him with increasingly bigger concentrations of energy).
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