The Nightmare Fuel page for all incarnations of Mega Man. Even the cartoon.
In order for Nightmare Fuel tabs to survive, a new writing style is going to be used, nicknamed Example Lobotomy. Basic rules: Just list facts as they are. Don't just say "character X" or "the X scene" (such zero context examples will be zapped). Spoiler policy to be determined on a case-by-case basis. Italics to be applied to works' names only and not to give emphasis on what tropers say. "X scared me" is already implied by the mere addition of that example by the troper.
The following entries have their own page:
The classic series had some at the end of 2 with the final Wily stage. A creepy cavern with what looks like blood or acid dripping from the ceiling, no music, and Dr Wily turning into an holographic alien, with only one weakness and the ability to kill you in 2 to 3 hits.
The overly darker and edgier Super Adventure Rockman's game over scenes. In the normal one, you watch helplessly as Roll dies, and Mega and Dr. Light hug in their last moments before Wily takes over the world. In the ending you get if you lose to the final boss, it electrocutes everyone, including Wily, to death.
Frost Man's ultimate goal in Mega Man 8 is to freeze Mega Man alive and eat him. Human Popsicle, no kidding.
In Mega Man & Bass, King proves he's not messing around by bisecting Proto Man with an axe.
Mega Man 9 has the fact that the game's Robot Masters were still active when Wily finds them in the scrap heap.
10's Endless Stage music; the echoes in the music sound eerily similar to what happens if Mega Man dies in the games.
What if we corrupt Mega Man 3? Or just use LUA Script that isn't meant for it? MEGA MAN GOES TO HELL!
What happens to the Servbots in so many battles (especially the first game) could really horrify people. The best example being the battle on the submarine (can't remember the name of the battle), when you're blowing up Bonne subs. With Servbots inside. Sure, they're "immortal" and we do see that they're okay later on, but until you do...
If you play Mega Man Legends and stay on the title screen then servbots walk past. Sometimes they're paper-thin!
Pretty much all of the dungeons in the Legends games have some Nightmare Fuel, especially the isolation.
The first boss in the game can be pretty scary for a kid. Not the boss design itself but how you're at the end of a long dark hallway, and you can just barely see a Reaverbot shooting you with rockets, and slowly inching it's way closer with absolutely no room to get behind him. You can kill him before he gets close though but still.
The sequel is not to be underestimated either. Forbidden Island has Reaverbots that suddenly grow giant skull-shaped heads when they attack you, and one of the dungeons has a giant skeletal Reaverbot menacing you, even suddenly crashing through a wall several times.
Mega Man Zero is much darker than the Classic series or even the X series of games, because the plot revolves around racist genocide and has one of the biggest monsters in gaming history as the main villain and the one responsible for the Crapsack World the series takes place in... and the games somehow got an E rating.
Mega Man Zero 4 also had the climactic final battle being composed of high octane nightmare fuel. For one thing, after Zero arrives at the core reactor of Ragnarok, Dr. Weil not only reveals himself to have survived, but you get a closeup of his face, which shows at least half of his face torn off with a mechanical skull revealing itself while grinning psychotically (as seen above), and he is even heard laughing demonically and maniacally. The fact that "Fate: Theme of Vile" (Dr. Weil's name was Dr. Vile in the Japanese version) is playing in the background also makes it even more tense, and it's even more frightening when hearing Dr. Weil's speech in the radio drama track taken directly from this scene.
Then, after merging with the core, the mood turns even more intense with the use of the song Fractured Border. Even after this form is defeated, the Ragnarok cannot be stopped from crashing, and then, when things couldn't possibly get worse, Weil reveals himself to have survived yet again, coming out of a hole in the floor. It's even more intense in the drama track where you not only hear Weil laugh before he speaks and reveals himself to have survived, but there is even sounds in the background that sounded more similar to a thunderstorm. Then he merges himself even further with Ragnarok with wires forcibly being shoved into him (The Drama Track even has Weil grunting in pain, indicating that the transformation process to be quite painful, and the Japanese version of the game even has it becoming a bloodbath while witnessing the transformation), and his completely merged form with Ragnarok looks even more horrific, with the Mega Man Zero Official Complete Works even referring to it as a "sinful abomination of a second form."
You know Ax-Crazy Omega from Zero 3? Destroyed 75% of Reploid life and 50% of humanity, and would have done more if he wasn't stopped? That was what Dr. Wily wanted Zero to be. If not for Sigma contracting the virus, it would have happened with the original Zero. Also a rare fusion of Nightmare Fuel and Fridge Horror.
Worse than that, it's not the first time this kind of thing happened in Megaman history. The Colony Drop of X5 is the canon ending of said game. That's right. That 75%/50% figure is from the remaining 10% that survived and procreated after X5.
Actually, the canon ending is the good ending. What really happened was that it was the debris that hit the area that made Area Zero and not the colony itself. The humans went underground to escape the pollution that leaked onto the planet's surface.
Zero 2's final boss' One-Winged Angel scene can shock you if you're not prepared for the scream.
Everything about Neo Arcadia, which is pretty much Nazi Germany under a different name. The Golems, the Eight Gentle Judges (who are anything but), and the Pantheons (especially the Zombie versions) are creepy as heck. And then there's Copy X...
At the end of Mega Man ZX you realize the basic plot stems from Japanese horror. Then early in the sequel ZX Advent there's the Tower of Verdure mission; you're trapped in a tower with a haywire security system while also being assaulted by a variety of weird plant monsters. This is only slightly creepy, but it leads up to the boss, Rospark. Pretty much everything this guy says, along with his voice, is seriously freaky. Of special note is "Come and cry in my bosom. Cry out in terror and pain!" And then, immediately after that fight, you have yet another encounter with the soul-sucking Artifact of Doom from the end of the first game.
Siarnaq. He is so not trusting of everything and traumatized by his past that he speaks in a monotone robotic voice. His personality, emotions and empathy have been completely removed just by whatever happened to him, leaving just his intelligence. Well, it's not entirely gone. He still has a little emotion left, only shown after he kills you.
And to top it all off, Dr. Weil may have had a hand in it as well.
Battle Network series
CircusMan.EXE of Battle Network 6. He captures the Cybeast and Mega Man with a vacuum, and in battles he can trap you under a circus tent while he pummels you.
The Ruby-Spears Mega Man cartoon had an instance of this in the first episode. In a flashback detailing Rock and Roll's creation, Dr. Wily had them strapped to an operating table to reprogram them. Via an electric drill to their heads. While they were awake. Complete with both of them struggling. It's the robot equivalent of a lobotomy, and we see the drill approaching from Rock's point of view.
Wily's line as he approaches Rock and Roll with the drill is unsettling.
Wily: A little tuck here, a little slice there, and you'll soon feel differently about this!
Also in "The Beginning", Wily warned Light not to follow him after he kidnapped Rock and Roll. If he did, Iceman would freeze him and Cutman would slice him up.
Wily's plans in "The Big Shake" and "The Day The Moon Fell" both involve causing extreme natural disasters, via earthquakes in the former and pulling the moon out of its orbit in the latter. They're played completely seriously.
Wily: I will create chaos! Destroy everything! Mankind will beg me to take over!
In "Electric Nightmare," Roll is battling a female cosmetics robot who gave her a bad facial. It's a fast fight, and cartoony until the end. Roll uses a buzzsaw to slice the robot in half across her stomach, her upper half falls to the floor, and then Roll vacuums her face off.
The Lion Men were not well-received, but they have one moment of genuine scariness. After zapping Dr. Light with his mind controlling lionizing Eye Beams, Tar turns his attention to Wily and turns him into a lion man as well. He then frisks him for his reprogramming device and zaps the Robot Masters with it, including Protoman and Roll, turning them all loyal to him.
The image of Rock/Mega on a lab table as a Terminator-esque endoskeleton in the intro is a little unnerving, even though it only shows up for a few seconds before dissolving into an image of Mega from that same position but with his "skin."
And there's the first nightmare in "Mega Dreams"; while the idea of Gutsman and Cutman pretending to be a couple may amuse you, that moment comes after a shot of a stuffed dino with what looks like blood on its muzzle.
In "Brain Bots", Wily places Mega Man in a Death Trap. The trap consists of a Descending Ceiling with spikes. Unlike some death traps, Mega was bound to the floor as it descended. What pushes this into Nightmare Fuel is what Wily said about it; he uses it to recycle robots he no longer needs into scrap metal. Meaning he's done this to his own robots.
What makes it worse is that some robots, like Fire Man and Star Man, were only in one episode and never seen or mentioned again.
Some of Cutman's lines fall under this. His Peter Lorre-esque voice makes it worse.
Cutman: I'll give them haircuts... from the neck up!
In "Bro Bots", Protoman's revelation as the Heel Face Mole is met with resistance. How does he control the heroes? By threatening to shoot the governor in the face.
Protoman: Power down, or I'll give Deacon a plasma shave!
In the same episode, Mega Man stumbles onto Wily's plan to create robot doubles of elected officials and control the city with them by finding a copy of Dr. Light. And given Wily had both Light and the governor suspended over a pit of acid, he may have been going for a Kill and Replace scenario.
Sometimes the Robot Masters (and Rush) are literally blown to pieces. This isn't too bad until one episode showed Roll in pieces, invoking the Uncanny Valley as Mega Man picks up her head to talk with it.
The show often used acid as a weapon, one time weaponizing acid rain; some kids became convinced that they'd die in an acid rain storm.
In "Curse of the Lion Men", Mega and Rush are about to be ground up at a salmon-canning company. They actually show the salmon hitting the saw blades.
While the episode involving Megaman and other robots "devolving" may be ludicrous (robots don't turn into caveman-like robots), it was still freaky seeing their gradual transformation.
"Bot Transfer" has Megaman and Snakeman swapping bodies, with an appropriately panicked reaction from the former. Their voices aren't mental, so Megaman is stuck with a snake's hiss as well as his body, and completely unable to get help; worse, his family doesn't suspect the "real" Megaman until the last second.
A lot of bad guys get broken into pieces (along the torso joints), including Fire Man being pulled apart by Roll's vacuum or someone getting bitten apart by Snake Man's weapon. Crystal Man gets his arm blown off at the elbow, and is still walking around like that until the end of the episode, and at one point Dark Man is reduced to a torso, half an arm, and his head, and he's STILL COMPLETELY AWARE OF THIS, even having to drag/hop around because no one will carry him when they run away at the end. Imagine if they did this to people for a second.
In Novas Aventuras De Megaman, Holzenbein specializes in robots. Said robots are made from homeless girls who were unfortunate enough to cross paths with them; they're held in a dark confinement area until it's their turn to be roboticized. Roll, or whatever her name was before Dr. Light saved her, was tricked into thinking that she'd simply be brought back to the park, this time among people who wouldn't smack her face off for playing with their kids. The next time we see her, she's been ripped apart and decapitated, her head (brain now exposed) sitting on a table as Wily talks about how she's the prototype for their newest humanoid computers. It would merely be "Persocoms, but horrible" if it weren't explicitly stated immediately afterward that most of these robots are forced into slavery—either in the Amazon as workers, or the "Suspended Cities" as prostitutes. Later on, we see more victims of this process, one of whom seems to be fully aware that she's de-limbed and floating in a culture capsule.
#12's cover and conclusion. Forget the nudity; those wires look rather invasive...Oh, and the gang is now at the mercy of this continuity's version of Protoman.
Adding to this are the small shots showing the full implications of a worldwide blackout. Examples shown are appliances and handheld devices failing, a ship being stranded at sea, cars crashing, an airplane diving out of the sky, and power going out at a hospital in the middle of surgery. It's safe to write off anyone who was on life support devices at the time.