Spider-Man is both Marvel Comics' most beloved and wholesome superhero. Since Peter Parker is almost always depicted as a teenager or a young adult, his villains tend to be around Peter's age or in similar places in their lives. Because of this, most of Spider-Man's villains are perfect for the mainstream Marvel Cinematic Universe. However, there are a few dark exceptions.
Certain Spider-Man villains were either so disturbing or even potentially offensive that it's highly unlikely that the MCU will ever acknowledge their existence. At best, these questionable villains need to be extensively reworked to fit the MCU. At worst, it would be arguably better for the MCU to simply ignore them forever.
10 Judas Traveler
Created by: Terry Kavanagh and Steven Butler
The Clone Saga (by Terry Kavanagh, Howard Mackie, and Gerry Conway) is one of the most controversial events in comic history. Besides being too convoluted to comprehend, it was an inconsequential arc that dragged on for too long. The almost-useless Judas Traveler perfectly embodied everything hilariously wrong with it.
Judas Traveler randomly appeared to spout ominous nothings. His habit of doing nothing to advance the story inspired controversy and ridicule. The MCU could fix the incredibly weird Clone Saga the way Spider-Man: No Way Home adapted One More Day (by J. Michael Straczynsjy and Joe Quesada), but Judas Traveler should be omitted.
9 Green Goblin III (Dr. Barton Hamilton)
Created by: Len Wein and Ross Andru
When Harry Osborn temporarily retired from being the Green Goblin, impostors rushed to fill the vacuum he left behind. One of these was Dr. Barton Hamilton, Osborn's psychotherapist who became obsessed with the Goblin persona. Dr. Hamilton was such an underwhelming and unpopular Goblin that he was permanently killed off.
Dr. Hamilton became "controversial" because of how uninteresting he was as Osborn's successor. Since the Goblins are meant to be Spider-Man's and Peter Parker's most personal enemies, having a random therapist steal the mask felt like a cheat. The MCU would be better off if it simply ignored Dr. Hamilton's Goblin phase.
8 Hobgoblin I (Roderick Kingsley)
Created by: Roger Stern, Mike Zeck, and John Romita Jr.
The Hobgoblin was intended to be the amoral billionaire Roderick Kingsley but at the last second, he was revealed to be Peter's friend Ned Leeds. This controversial change ruined Hobgoblin and Kingsley so much that they've been stuck in the D-list ever since. Interestingly, Leeds' villainous turn endured as a fan-favorite twist.
The MCU already introduced its version of Ned. Fans and Ned's actor (Jacob Batalon) expressed interest in seeing him become the Hobgoblin. Ned being the Hobgoblin would be a great nemesis for the MCU Spider-Man. Using Kingsley instead would be both unpopular and an uninspired retread of Willem Dafoe's Norman Osborn.
7 Gabriel & Sarah Stacy
Created by: J. Michael Straczynski and Mike Deodato Jr.
The only thing more controversial than Norman Osborn and Gwen Stacy having a one-night-stand was them having children. The twins Gabriel and Sarah were conditioned to kill Spider-Man and despise Peter from birth. They were hated so much that not only were they revealed to be laboratory-made clones, but they were quickly killed off.
Besides the fact that the MCU currently doesn't have a Norman or Gwen (plus her dark comic ending), Gabriel and Sarah carry so much baggage. For one, they have an implied incestuous relationship. It's also currently impossible to rehabilitate either of them because of their inseparable personal connections to Spider-Man and those closest to him.
6 Superior Spider-Man
Created by: Dan Slott and Ryan Stegman
When Doc Ock swapped bodies with Peter Parker to become the "Superior Spider-Man," readers were split. Some loved this seismic status quo shift, while others hated it. It wouldn't be wrong to expect a similar reaction to such a controversial twist if ever the Superior Spider-Man made his way into the MCU.
Turning a beloved character evil or recasting them are two of the most controversial things a major franchise like the MCU could do. The Superior Spider-Man effectively does both. If the MCU ever introduces the Superior Spider-Man, the best they hope for is that audiences eventually warm up to him the way comic readers did.
5 Hypno-Hustler
Created by: Bill Mantlo and Frank Springer
Hypno-Hustler's biggest problem is that he's an anachronism. Not only was he based on the old disco wave, but he's also a collection of the most obvious stereotypes of Black people from the 70s. Although he wasn't made to offend and was well-received during his prime, Hypno-Hustler can come across as borderline racist today.
Later on, Hypno-Hustler was demoted from a decent foe to a joke. Some theorized Marvel did this to obscure him without killing him. A non-MCU Hypno-Hustler movie is now in development. It wouldn't be surprising if it was a 70s-era period piece, or a contemporary story with many changes done to Hypno-Hustler's original depiction.
4 Massacre
Created by: Dan Slott and Marcos Martin
Massacre was one of those recent Spider-Man who was so dark and violent that they felt misplaced. Massacre was basically the Punisher (who arguably creates his own worst enemies) as a villain. He had no motive to his rampages. He also blamed his evil on the shrapnel lodged into his brain, which stopped functions like feeling emotion.
Even ignoring that Massacre is yet another edgy and unoriginal gun-wielding villain, gun violence is a highly controversial and terrifying reality today. Massacre's lack of redeeming qualities and interesting characterizations also work against the case to adapt him. It's highly unlikely that the MCU will adapt Massacre any time soon.
3 Skinhead
Created by Gerry Conway and Alex Saviuk
Like every other Marvel hero, Spider-Man has a few Nazi villains. One of the most offensive, however, was the unsubtly named Skinhead. What made Edward Cross different from Nazi villains like the evil and influential Red Skull was that he was born into a Jewish family. Cross hated himself so much that he grew up into a Neo-Nazi.
Besides Cross' problematic backstory, he was worse when he became a superpowered bigot. Skinhead was so controversial that he was never seen or mentioned after one major appearance. For better and worse, the MCU watered down the comics' darkest villains, like the Red Skull. Skinhead is arguably too hateful to even tone down for live-action.
2 Freak
Created by: Dan Slott and Steve McNiven
Conceptually, Freak fit the theme of Spider-Man's villains. He was an ordinary person who accidentally became superhuman thanks to a science experiment gone awry. However, Freak's origins and motives are highly insensitive. To wit, Freak was a nameless drug addict who injected himself with an experimental serum he mistook for meth.
Freak was such an addict that he still chased drugs even after becoming a rotting monster. Freak embodied the most obvious and offensive stereotypes of drug addicts. It's hard not to see him as a conservative cautionary tale and dehumanization of such people. The MCU would be wise to ignore Freak the way the comics did.
1 Norman Osborn
Created by: Stan Lee and Steve Ditko
As evil and terrifying as he was in the movies, the live-action Green Goblin was heavily toned down from his comic self. Originally, Norman Osborn was monstrous from the very beginning. The Goblin Serum only exacerbated what was already there. Osborn courted controversy and notoriety for the atrocities he committed over the decades.
Osborn and the Goblin indulged in cruelty because they loved being evil. A good example of this is everything he did to Gwen Stacy. Conversely, his live-action version always split Osborn's good nature from the Goblin's evil. Given the MCU's family-friendly approach, accurately adapting Osborn would be ill-advised and controversial.