Spider-Man is not usually associated with the horror genre, but if one particular comic book villain is to come to the screen, it could only work as part of Sam Raimi's Spider-Man 4, starring Tobey Maguire as Peter Parker. The project was in development by Sony after the release of the controversial Spider-Man 3, also directed by Raimi, but it was cancelled in favor of The Amazing Spider-Man reboot. However, if Sony want to use one horrific Marvel story-line and character, it would need Raimi at the helm to make it work.
"Man-Spider" refers to a mutated Peter Parker, who has become a horrific hybrid of human and arachnid. The comic books have seen Peter transform into Man-Spider a few times, such as when he and X-Men member Angel are transformed into animalistic forms by Brainchild, or when the villain known as "the Queen" turns Peter into a literal giant spider. However, perhaps the character's most famous appearance is in the animated series from the '90s simply titled Spider-Man, which sees Peter's mutation destabilize. A whole arc is devoted to the issue, as Peter seeks help from Dr. Curt Connors/The Lizard, Charles Xavier, and Hank McCoy - though he eventually grows four extra arms. A fight with Frank Castle and Michael Morbius escalates his transformation into Man-Spider which is only reverted by the combined efforts of Kraven the Hunter, Dr Mariah Crawford, and the Punisher.
As a horrific body horror transformation, the only movie adaptation that could ever do Man-Spider justice is Sam Raimi's Spider-Man 4. Raimi is a highly experienced horror director, having developed the Evil Dead trilogy starring Bruce Campbell. His Spider-Man trilogy is also filled with moments of horror, such as the birth of Doctor Octopus in Spider-Man 2, which sees a team of doctors massacred. The director has also proven that he can make a full superhero horror movie with 2022's Doctor Strange in The Multiverse of Madness, which turns former Avenger Wanda Maximoff into a slasher villain. With this in mind, Raimi is the perfect director to bring Man-Spider to life.
Tobey Maguire's Peter Parker is also well set up to transform into Man-Spider. The Peter of the Raimi series is already closer to a spider than his counterparts, Tom Holland and Andrew Garfield, a plot point even acknowledged in Spider-Man: No Way Home as the Peters watch in awe as Tobey's Peter produces organic webbing from his wrists. It therefore would be easy to accept that Peter's mutation was accelerating, transforming him into Man-Spider. Raimi could even tweak his initial script for Spider-Man 4, which features the Vulture/Adrian Toomes as its main villain. The Vulture ultimately accidentally absorbs the Man-Spider mutation from Peter after trying to drain his youth in Spider-Man, so this plot point could easily be worked in Spider-Man 4's script.
As a more stylistic, horror-focused superhero series, the Raimi universe is the perfect place to explore Man-Spider on film. Tom Holland's Peter Parker is far too marketable to spend half the movie as a giant Cronenbergian monster, but Sony could take the chance on a rebooted Tobey Maguire-led series. This would allow for not only a triumphant return of Maguire and Sam Raimi to the Spider-Man series, but also a new selection of Spider-Man movies running parallel to the Marvel Cinematic Universe, thanks to the multiverse. Raimi's films would be much darker, allowing him to really flex his horror auteur muscles. Bringing back Raimi and Maguire to the Spider-Man universe is the perfect way to bring Man-Spider to the screen and finally revive the cancelled Spider-Man 4.