The latest trailer for Spider-Man: No Way Home continues to provide fans with questions about the true motivations of Doctor Strange in the movie. Some think he could be the villain, which wouldn't be out of the question. Doctor Strange has actually been a villain on numerous occasions in Marvel Comics before, including what is technically his first appearance.
A fan theory about Doctor Strange being an imposter in the movie has been circulating since the first trailer dropped, and that could be the case since it's happened in the comics. If Doctor Strange does turn out to be a villain in the movie, the comics likely harbor some clues as to how it will ultimately play out.
Doctor Carlo Strange
Comic book fans know Doctor Strange first appeared in Strange Tales #110 in 1963, but many may not know that there was a Doctor Strange before him, and he was a villain. Doctor Carlo Strange preceded Stephen Strange by a few months in Tales Of Suspense #41. The two characters have no relation and were created independently of each other.
Carlo Strange was a mad scientist who fought Iron Man in the story. He used a variety of gadgets and inventions to accomplish his goals, including a mind-control device.
Planet Hulk
One of the biggest modern examples of Doctor Strange behaving in a way that is at least morally questionable led to the Planet Hulk storyline. As part of the secret Illuminati group of superheroes including Namor, Black Bolt, Iron Man, Reed Richards, and Professor X, Doctor Strange conspired to exile the Hulk off Earth after a tragic incident in Las Vegas.
The Hulk needed to be dealt with, but the summary exile of the character, with no care for his well-being or the consequences, lacked any empathy or good intent. The price was stark, as Hulk eventually returned to wreak havoc on the Avengers and the world.
Ally Of Dormammu
Dormammu is one of Doctor Strange's greatest villains, if not the greatest. That's why it was such a shock for fans to see Doctor Strange the willing ally and disciple of Dormmauu. This shocking turn happened in What If? #18, when one of the most powerful variants of Doctor Strange disregarded any sense of right or wrong and pledged himself to Dormammu.
He killed Baron Mordo after Mordo taught him dark magic. Much like his counterpart in the animated What If..? series, this version of Strange had no compunction about consuming darker and darker magic.
Marvel Zombies
Another evil version of Doctor Strange was not so willing. In the Marvel Zombies universe in the comics, soon to become its own animated series on Disney+, Doctor Strange was one of the last superhero holdouts against the zombie plague. He eventually succumbed, becoming a zombie master of the dark arts.
As a zombie, he is part of the all-out assault on the castle of Doctor Doom, and is later in league with the zombie Kingpin, using his magic to allow the villain to perceive other universes.
Dark Double
A lot of the speculation about Doctor Strange in No Way Home is that he is an imposter or perhaps some kind of double. A dark double of the Sorcerer Supreme does exist in the comics. In Doctor Strange #6 from 2018, the real Strange returns from outer space to find a perfect copy of himself living in the Sanctum Santorum.
The double was up to no good, mostly due to the dark influence of Baron Mordo. This evil Doctor Strange turns out to be a character named Casey Kinmont, who had been a pupil of Strange some time before.
Cancerverse
The Doctor Strange of Earth-10011 is one of the evilest versions of the character in comics. He became an agent of the Many Angled Ones from the Cancerverse after his reality was completely consumed by these natural enemies of the alien symbiotes that spawned Venom. Strange aided them in their conquest of other realities, including Earth-616.
Doctor Strange was part of a corrupted version of the Defenders that fought the Guardians of the Galaxy as the invasion began. He was destroyed by Thanos, along with the rest of the Defenders.
Dormammu's Apprentice
Doctor Strange became Dormammu's apprentice once again, this time unwillingly and in the main Marvel Universe of Earth-616. When Dormammu succeeded in defeating Eternity, one of the most powerful cosmic beings in the Marvel Universe, he altered reality so that Doctor Strange became his servant.
This wasn't the real Doctor Strange, though. The real Sorcerer Supreme took the battle directly to his counterpart in a preview of what's to come in the MCU if the imposter theory holds true.
Doctor Strange has battled all kinds of mystical creatures in his time as the Sorcerer Supreme. In one major battle, he becomes one of those creatures and a villain at the same time. Strange sought help to save the life of his lover, Clea, in Marvel Team-Up #80. In exchange for help from the sorceress Marie Laveau, he was transformed into a werewolf.
As a werewolf, Doctor Strange nearly lost all sense of himself. He attacked both Clea and Spider-Man, who had agreed to help him in his mission. He only reverted back to humanity after the sacrifice of Satana.
Secret Wars
Doctor Strange is one of the most powerful magicians in the Marvel Universe, but even he couldn't compete with the power of God Emperor Doom. In the 2015 version of Secret Wars, Doctor Doom alters reality so his nemesis Strange is one of his most trusted allies and a major villain in his own right.
Doctor Strange became Sherrif Strange, the chief lieutenant of Doom on Battleworld. He carried out his often heinous orders without fail. He ultimately redeemed himself, helping the surviving heroes undermine Doom and restore reality.
The Necromancer
One of the most villainous versions of Doctor Strange in the comics, and perhaps the most likely to appear in the MCU, is the Necromancer. This alternate version of the character appeared in Doctor Strange, Sorcerer Supreme #46 as an evil variant who completely embraced the dark arts after killing Baron Mordo.
Somewhat like the What If..? version from the MCU, the Necromancer had been trapped in a pocket of reality within the being of Eternity, but he then escaped to continue his pursuits in Earth-616.