Why Mysterio's Return Wouldn't Have Worked In No Way Home
Concept art for Spider-Man: No Way Home reveals Mysterio almost made his return in the movie - but it really wouldn't have worked. In 1964, Stan Lee and Steve Ditko teamed up for The Amazing Spider-Man annual - an epic story in which six of Spider-Man's greatest foes united as the Sinister Six. The supervillain team has become a staple of Spider-Man lore ever since, and Sony has long been interested in bringing them to life on the big screen. Given Spider-Man: No Way Home featured Green Goblin, Lizard, Sandman, Doctor Octopus and Electro - five of the Sinister Six - many viewers assumed there was a final villain who was being concealed.
Recent concept art for Spider-Man: No Way Home has revealed there almost was a sixth supervillain: Mysterio, shown battling Doctor Strange. Mysterio's return would have completed the Sinister Six, although it's unclear exactly how he would have come back. It easily might have been a Mysterio from an alternate dimension where he really was a sorcerer, explaining why he could go head-to-head with Doctor Strange. It might have been the Mysterio from the MCU plucked from the past, moments before his death. Or - in what is perhaps the most intriguing possibility of them all - it could have been the MCU's Mysterio, revealed to have faked his own death at the end of Spider-Man: Far From Home.
Whatever the case may be, though, Mysterio's return simply wouldn't have worked. The core problem is that, thematically, Mysterio is totally different from the other villains who appeared in Spider-Man: No Way Home (which is likely why the MCU's Vulture didn't make the cut either). Every one of them had been caught up in some sort of experiment gone wrong, one that had granted them remarkable powers but also affected their minds or exacerbated previously-held quiet desperation. None of them initially started out intending to be villains. In contrast, Mysterio was motivated purely by revenge against Tony Stark and a lust for power. There was nothing to "cure" him of, meaning he couldn't be treated like the others.
This disparity of intent would have been particularly problematic if Mysterio was indeed intended to be plucked from the end scenes of Spider-Man: Far From Home. With the others, Spider-Man successfully changed their destinies by curing them before they returned to their own timelines - effectively creating multiple new timelines in Spider-Man's MCU multiverse. But because Mysterio couldn't be treated, Spider-Man would have been sending Quentin Beck back in time to die. Mysterio's death in Spider-Man: Far From Home was an accident, but it would have thus been transformed into an intentional act on Spider-Man's part. Spider-Man would indeed be directly responsible for Mysterio's death.
Making matters worse, any sighting of Mysterio, whether during the Statue of Liberty battle or before it, would have destroyed the narrative thread running through Spider-Man: No Way Home. The world would have seen Mysterio and realized Peter Parker hadn't actually been responsible for his death at all. Mysterio's presence would have been seen as supporting Spider-Man's case that he was innocent, and J. Jonah Jameson's hate campaign against him would have collapsed. That would have made the ultimate resolution of Spider-Man: No Way Home feel rather disjointed. So, Marvel and Sony were wise to scrap Mysterio, allowing the story to flow much better.