5 Terrible Things Mister Sinister Has Done to the X-Men Before Making His MCU Debut

Skip to content Mister Sinister is coming to the Marvel Cinematic Universe, and this was announced when Adam Driver broke the news himself at D23. The first X-Men movie in the MCU will hit theaters in May 2028, and Kevin Feige referred to the next phase as the Mutant Era. There is no word on what these stories will entail, as Marvel has only announced a few of the mutants who will be on the official X-Men team, but with Avengers: Doomsday and Avengers: Secret Wars coming first, there is a lot to figure out before the X-Men’s new era in the MCU starts.

While the best Mister Sinister stories offer plenty of options for the MCU, there are some terrifying things he was responsible for that could create great X-Men stories on the big screen. From corrupting heroes and manipulating children to mass murder, here are the most devastating things that Mister Sinister ever did to the X-Men.

Mister Sinister has been obsessed with Cyclops since Scott Summers was a child. These stories were originally told in Classic X-Men #41-42 (1989) by Chris Claremont and Mike Collins. The stories followed Scott after his parents’ apparent death when he was placed in an orphanage in Nebraska called the Syate Home for Foundlings. While there, another child named Nate bullied him relentlessly, and it turned out that the boy was a disguise used by Mister Sinister, who ran the orphanage. It remains interesting that Nate was the name Scott and Madelyne Pryor gave to their own child.

It was also later revealed that Mister Sinister experimented on a young Scott while he was in a coma after the accident that killed his parents. Scott’s entire life was built on trauma and tragedy, and it is what turned him into the great X-Men leader he became, but also what makes him such an unlikeable character in Marvel Comics. There were several stories that really explored Sinister’s machinations, including The Further Adventures of Cyclops and Phoenix miniseries.

Mister Sinister has done some terrible things in Marvel Comics, and he has been a threat to mutants even years before the X-Men ever formed. This goes all the way back to his experiments in World War II. Sinister was a Nazi scientist at Auschwitz, and he was nicknamed Nosferatu by the prisoners while he worked alongside Josef Mengele, the real-life Nazi scientist who experimented on camp inmates. Mister Sinister’s experiments were all focused on genetics, which then carried over into the modern era, when he specialized in cloning. Auschwitz connected him to Magneto in the most terrible way.

There was one future X-Men member who Mister Sinister confronted in World War II, when he reportedly collected Namor’s blood and cloned him as Experiment N2. This put Mister Sinister in the Invaders’ sights during the war. An important connection to the MCU is that Mister Sinister left the war and changed his name to remain hidden after working with the Nazis. The name he chose was Dr. Nathan Milbury, the name Adam Driver mentioned when he announced he was joining the MCU. As Milbury, he encoded his psychic matrix into mutants like Charles Xavier and Sebastian Shaw.

After Jean Grey died, Scott Summers met Madelyne Pryor, a woman who had an uncanny resemblance to Jean, and he ended up falling in love with her. After losing his leadership role in the X-Men to Storm, he left with Madelyne and started a new life in Alaska with their child, Nathan Summers. It looked like he was going to have a peaceful life away from superhero duties. But that all changed when Jean Grey was found still alive, and when Scott went to her, Madelyne and Nate were attacked by the Marauders. She was almost killed, and Nate was abducted.

That was tragic, but things got worse. Madelyne Pryor wasn’t even a real human. She was a clone Mister Sinister created, a failed project until a piece of the Phoenix Force went into her body and she gained sentience. Scott going back to Jean and the abduction of Nate drove Madelyne over the edge, and when she realized she was a clone, she turned pure evil and became the Goblin Queen and almost destroyed the world in “Inferno.” Mister Sinister was to blame for everything.

The most important crossover series for Mister Sinister in the Krakoa Era was “Sins of Sinister.” This was an event that kickstarted the end of Krakoa, as what happened in this series led into the “Fall of X” storyline. This was a 2023 crossover series by Kieron Gillen, Al Ewing, Si Spurrier, and various artists, and it all ended with “Sins of Sinister: Dominion.” This was an interesting storyline because it took place in three different eras, including 10 years, 100 years, and 1,000 years in the future.

Mister Sinister implanted his genetic code into Krakoa’s population of mutants and created the Moira Engine, which was a set of Moira MacTaggert clones, and since her death resets timelines, he was able to constantly experiment and manipulate things until he was able to get the future to look the way he wanted. Mister Sinister even killed the most important members of the Quiet Council, and it took Moira destroying the Moira Engine to restore Krakoa, leading the Quiet Council to banish Mister Sinister to the Pit.

The worst thing that Mister Sinister ever did happened before he even appeared in Marvel Comics. The “Mutant Massacre” took place in 1986 across several titles, including all the X-Men series, as well as Thor, Power Pack, and Daredevil. Chris Claremont, Louise Simonson, Walter Simonson, John Romita Jr., and Sal Buscema acted as creators on the story, which saw a villainous group called the Marauders go into the tunnels under New York City and begin slaughtering the Morlocks who lived there. Very few survived, and even X-Men like Angel, Kitty Pryde, Nightcrawler, and Colossus suffered great injuries.

While Mister Sinister didn’t debut until 1987, it was revealed that he ordered the Marauders to kill the Morlocks to cover up past experiments that Dark Beast conducted. Gambit was the mutant who led the Marauders into the tunnels, not knowing they were planning to kill all the mutants there. This remains one of the deadliest attacks in X-Men history, and it was a despicable moment when Mister Sinister proved that he only saw these innocent mutants as failed lab rats that he could throw away when they no longer served a purpose.

What are your favorite Mister Sinister stories from Marvel Comics? Let us know what you want to see when Sinister arrives in the MCU in the comments below.