Mysterio could also be a main antagonist. He could use his illusions to make Spider - Man doubt himself and the reality around him. He could create elaborate schemes that make it seem like Spider - Man is the bad guy, turning the public against him while he tries to carry out his real motives, which could be anything from stealing valuable technology to getting revenge on someone in the city.
Venom is another strong candidate. The symbiotic relationship between Eddie Brock and the alien symbiote could be explored in a new and darker way. Venom could be more powerful and more bloodthirsty, constantly hunting Spider - Man and trying to take over his life. His presence could also introduce an element of horror to the fanfiction.
The Green Goblin would be a great main antagonist. His chaotic and unpredictable nature could pose a real threat to Spider - Man. He could have a new and improved glider and pumpkin bombs, and his goal could be to take over the city by causing mayhem and destruction.
The Green Goblin would be a great choice. He's always been one of Spider - Man's most dangerous foes. With Spider - Man unmasked, the Green Goblin could use this to his advantage, attacking not just Spider - Man but also those close to him, knowing that Spider - Man will be more vulnerable because he has more to lose now.
Doctor Octopus could be a great main antagonist. He could upgrade his mechanical arms and team up with other villains. His intelligence and his ability to create complex machines could pose a serious threat to the Avengers and Spider - Man.
It could be the Green Goblin. He's always been a major foe of Spider - Man and might be the reason for Spider - Man to fake his death, like if he's planning a huge attack and Spider - Man needs to deceive him to stop it.
The Green Goblin could be a great main antagonist. He has a long - standing feud with Spider - Man. Maybe in this fanfiction, he could be out for a more brutal revenge after a particularly humiliating defeat. He could target Spider - Man's loved ones or try to completely destroy his reputation in the city.
The Green Goblin could be a great main antagonist even in a Spider Man reborn story. Maybe in this version, he has developed a new form of insanity - inducing gas that affects Spider Man's new powers. Another possibility is Doctor Octopus. He could have found a way to merge his mechanical arms with some sort of alien technology, making him far more powerful and a real threat to Spider Man reborn.
It could be a corrupted version of an old ally. For example, a former S.H.I.E.L.D. agent who was exposed to some strange space radiation. This has turned him evil and he now wants to use his knowledge of Earth and his new - found space powers to create chaos. He blames Spider Man for not being able to save him from the radiation and is determined to make Spider Man pay, all while causing destruction across the galaxy.
Perhaps Doctor Octopus. But instead of just having mechanical arms, his mutation gives him the ability to control any metal object in the city. He wants to take over the city using his newfound powers and sees Spider - Man as the only obstacle.
How about a new villain created specifically for the fanfiction? A being made up of the combined negative energy from all the spider - verses. This entity could be called the 'Void - Spider' and it feeds on the chaos and destruction that often follows Spider - Man in his battles. It would be a very powerful and unique threat that the Spider - Men from different universes would have to face together.
Another option for the main antagonist in the fanfiction could be a jealous classmate. This classmate might be envious of Spider Man's popularity and powers. He or she could try to sabotage Spider Man at school, like spreading rumors about him or trying to get him in trouble with the principal. This would make Spider Man's school life even more difficult as he has to deal with both this classmate and any real threats to the city.
It could be the Green Goblin. In the sequel, he could return more powerful and with a new plan. Maybe he has found a way to enhance his strength and insanity using some new Oscorp technology. He could target Spider - Man not only for revenge but also to prove his superiority over the web - slinger.