Some Marvel villains are just outright too terrifying to appear in the Marvel Cinematic Universe as it currently stands. The MCU timeline has long been known for delivering thrilling superhero action packaged within a PG-13 framework. As a result, some monstrous Marvel foes would be considered far too horrifying to appear in the MCU.

The MCU has primarily delivered PG-13 projects. However, recent developments suggest that the franchise is slowly opening the door to darker and more terrifying storytelling. With Agatha All Along embracing supernatural horror and ᴅᴇᴀᴅpool & Wolverine becoming the MCU’s first R-rated film, the MCU’s future could feasibly venture further into genuine horror, which many of these characters would be ideal more. If the MCU were to include them in the franchise’s current tone, their sheer horror elements would likely need to be toned down to be palatable for all audiences.

10

Mr. Smile & Mr. Sulk

First Appeared In Dr. Strange #5 (July 2020)

Few Marvel villains evoke pure horror quite like Mr. Smile and Mr. Sulk. These unsettling figures, introduced in Dr. Strange #5, look like they crawled straight out of a horror movie. Mr. Smile is a gaunt, grinning nightmare with razor-sharp teeth, while Mr. Sulk is a hulking brute with a featureless face. Their entire presence feels like something from a psychological horror film, making them one of the most genuinely frightening duos in Marvel’s history.

Bringing Mr Smile and Mr Sulk into the MCU would require embracing a full-fledged horror aesthetic – akin to It or The Babadook. Their designs alone could push a PG-13 rating to its limits, and their eerie, silent menace would set them apart from the MCU’s usual rogues’ gallery. If Marvel Studios ever decides to fully embrace horror, these two could make for haunting, unforgettable villains.

9

Madcap Can Induce Madness

First Appeared In Captain America #307 (July 1985)

Madcap is one of the most disturbing villains Marvel has ever created. A man who lost his entire family in a tragic accident, he was exposed to a chemical that granted him an unbreakable healing factor and drove him completely insane. His powers extend beyond mere resilience – his very presence can induce madness in others. In some stories, his influence has driven people to suicide, making him an especially unsettling figure.

Later iterations of Madcap take his horror elements even further, particularly after his monstrous face is reveled. At one point, he bonds to another character’s stomach in a grotesque, body-horror twist reminiscent of Malignant or The X-Files. While the MCU could tone down his more extreme elements, his core concept – a walking manifestation of insanity – would still be a tough sell in a franchise that typically blends comedy with its darkness.

8

The Brood Are The X-Men’s Scariest Foe

First Appeared In The Uncanny X-Men #155 (March 1982)

If the Alien franchise ever had a crossover with Marvel, it would look exactly like the Brood. Introduced as one of the X-Men’s most dangerous threats, the Brood are insectoid parasites that implant their eggs inside living hosts, slowly transforming them into monstrous new Brood drones. Artist Dave Cockrum has stated that he designed the aliens as the most horrible looking thing he could conceive.

The horror parallels to Xenomorphs from Alien are impossible to ignore – especially considering that the Brood’s reproductive process is even more terrifying, with the victim retaining their intelligence as their body mutates into a grotesque, insectoid form. While the MCU is set to introduce the X-Men, the Brood’s sheer body horror and nightmarish design might make them a tough fit for the franchise’s lighter tone. Indeed, the Brood’s appearance in X-Men: TAS was so toned down the monsters lost their mystique.

7

Arcade Is A Theatrical Hitman

Marvel Team-Up #65 (January 1978)

While Arcade might not seem as outwardly terrifying as some of the other villains on this list, his methods place him firmly in horror territory. A sadistic ᴀssᴀssin, Arcade doesn’t just kill his targets – he traps them in elaborately themed death games inside his personal playground of horror, Murderworld. Essentially a PG-13 version of Saw, Arcade’s lethal amusement park is filled with ᴅᴇᴀᴅly contraptions and psychological torment.

Whether it’s trapping the X-Men in a giant pinball machine or forcing his victims to navigate rooms filled with lethal surprises, Arcade’s brand of villainy is equal parts theatrical and sadistic, often sporting an extremely unsettling rictus grin. While the MCU could adapt him more comedically, a fully realized Murderworld would require embracing a much darker tone. Undoubtedly, a comic-accurate Arcade might be too intense for Marvel’s usual family-friendly approach.

6

Styx The Living Cancer

First Appeared In Amazing Spider-Man #309 (July 1988)

Styx is a horrifying villain who embodies pure death and decay. Once a reanimated corpse, he possesses the ability to instantly rot and kill all organic matter with a single touch. His grotesque power makes him one of the most terrifying figures in Marvel lore, as even a brief encounter with him could mean instant death.

Styx’s appearance is equally disturbing, with a cadaverous, almost skeletal form that reinforces his grim nature and long gnarled fingers he can extend at will. Unlike other Marvel villains who rely on weapons or strategic planning, Styx’s mere existence is a death sentence for those around him. Adapting him into the MCU would be a challenge, as his rotting touch and ghastly presence push the boundaries of PG-13 horror. If Marvel ever ventures into full-fledged supernatural terror, Styx could be one of its most chilling additions.

5

Freak AKA Armadillo Man

The Amazing Spider-Man #552 (March 2008)

Freak, also known as Armadillo Man, is a truly grotesque character whose very existence is dreadful. While seeking drugs, Freak accidentally injects himself with Dr Curt Connor’s animal genes. This triggers several evolutions wherein his skin comes away and reveals an armadillo-like creature with bullet-proof skin. His transition as a monstrous, skinless man with exposed muscle proffers a horrific visage. This makes him one of Marvel’s most unsettling figures.

Freak’s ultimate transformation into a near-mindless brute with extreme durability and an ability to adapt to conditions made him incredibly difficult to stop. Unlike the more stylized horror of villains like Green Goblin, Freak’s design leans into raw body horror, reminiscent of grotesque creatures from films like The Fly or Hellraiser. The sheer grotesqueness of his exposed flesh would likely be too intense for a standard MCU release.

4

The Thousand Is An Arachnophobe’s Biggest Nightmare

First Appeared In Tangled Web: The Thousand #1 (May, 2001)

The Thousand is an enтιтy straight out of a horror film. Originally a man named Carl King, he became a hive mind of spiders after consuming Peter Parker’s radioactive spider. This resulted in his body being completely overtaken by the arachnids, allowing them to infiltrate and possess human hosts. The sheer nightmare fuel of a swarm of sentient spiders using human bodies as puppets makes The Thousand one of the most terrifying villains in Marvel history.

A scenario where an innocent person is reduced to nothing, but a hollow husk controlled by countless arachnids is truly a horrifying concept. As is the Thousand’s emergence from a host body, which typically involves teeth falling out or eyes being torn open as spiders claw their way out, killing the host. This makes him one of Spider-Man’s most terrifying foes.

3

Skinless Man Is Straight Out Of A Horror Movie

First Appeared In Uncanny X-Force #21 (February 2012)

Skinless Man is exactly what his name implies – a horrifying villain stripped of his flesh, revealing a grotesque, sinewy figure that is the stuff of nightmares. Once a former British barrister named Harry Pizer, he became embroiled in the Weapon Plus program. There he was subjected to a horrific punishment that left him alive but without skin.

The Skinless Man’s appearance is reminiscent of Frank from Hellraiser, with his gruesome, skinless form making him one of the most visually unsettling villains in Marvel history. A character like this would be nearly impossible to adapt into the MCU without severely toning down his horrific nature. If Marvel ever embraces a full horror aesthetic, Skinless Man could be a truly terrifying addition, but his grotesque design makes him unlikely to appear in the franchise as it currently exists.

2

Demogoblin Is A Monstrous Goblin Villain

First Appeared In Web Of Spider-Man #86 (March 1992)

Demogoblin takes the already terrifying concept of Spider-Man’s Goblin villains and amplifies it with pure demonic horror. Initially, the Demogoblin is the persona created when Hobgoblin’s essence was fused with a demon. The resultant monster soon separated from Hobgoblin, retaining a hellish, skeletal visage and an eerie, sickly glow. Unlike the traditional Goblin enemies, Demogoblin isn’t motivated by greed or revenge but by supernatural zealotry, seeking to purge the world of sinners in the most violent way possible.

The Demogoblin is armed with the Goblins’ signature pumpkin bombs but also deploys his own that a despair and suffering in their victims. This adds a distinctly psychological horror element to his already monstrous persona. While the MCU has introduced a Green Goblin, Demogoblin’s outright demonic nature would push the franchise into much darker territory than it has ever gone before.

1

Carrion Is A Walking Plague

Spectacular Spider-Man #25 (December 1978)

Carrion is the living embodiment of a ᴅᴇᴀᴅly plague. Created by the geneticist and Spider-Man foe Miles Warren, AKA the Jackal, Carrion has reappeared under several guises – though always with a disfigured appearance and the ability to decay and wither anything he touches. Over time, his mutation worsened, transforming him into a walking virus that could spread contagion at an alarming rate.

What makes Carrion especially terrifying is his ability to reduce people to dust with just a touch, making him a nearly unstoppable force of destruction. His later transformation into a sentient virus, capable of infecting others and spreading himself like a disease, makes him even more horrifying in a post-COVID world. His plague-like abilities and devastating touch make him one of Marvel’s most unsettling villains—one that might be too intense for mainstream MCU audiences.

Upcoming MCU Movies

• 
  
  

  
  

  Thunderbolts*

  Release Date

  
  May 2, 2025
  

  
  
  
  

  
  

  Powered by

  
  

  
  Expand
  Collapse
  

• 
  
  

  
  

  The Fantastic Four: First Steps

  Release Date

  
  July 25, 2025
  

  
  
  
  

  
  

  Powered by

  
  

  
  Expand
  Collapse
  

• 
  
  

  
  

  Avengers: Doomsday (2026)

  
  
  
  
  

  
  

  
  Powered by

  
  

  
  
  Expand
  Collapse
  

• 
  
  

  
  

  Spider-Man Homecoming 4

  Release Date

  
  July 24, 2026
  

  
  
  
  

  
  

  Powered by

  
  

  
  Expand
  Collapse
  

• 
  
  

  
  

  Avengers: Secret Wars

  Release Date

  
  May 7, 2027
  

  
  
  
  

  
  

  Powered by

  
  

  
  Expand
  Collapse