Well, in the Spider - Man universe, one common factor could be personal tragedy. Maybe the person lost someone dear due to Spider - Man's actions, whether intentional or not. For example, if a bystander was accidentally hurt during one of Spider - Man's battles and that person was a loved one of the future villain, it could fuel their hatred and desire for revenge. Another aspect could be envy. Spider - Man has all these amazing powers and is adored by the public. Someone who feels overshadowed and unappreciated in comparison might turn to villainy just to prove themselves and get the attention they think they deserve.
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.
The Green Goblin could be the villain. He could have developed a new type of pumpkin bomb that explodes with a force that seriously injures Spider Man. This would be in line with their long - standing rivalry in the Spider - Man universe.
Doctor Octopus, or Otto Octavius, was a brilliant scientist. His over - ambition in his scientific experiments led to a fusion of his mechanical arms with his body. This accident drove him mad, and he turned to a life of crime, using his powerful tentacle - like arms to rob and cause destruction, seeing Spider - Man as an obstacle to his plans.
Well, Norman Osborn was a brilliant but egotistical man. His company was facing tough competition, and he was desperate to prove himself. He experimented on himself with a dangerous chemical compound. This not only gave him superhuman strength and agility but also split his personality. As the Green Goblin, he became a sadistic villain. He first targeted Spider - Man because he saw the web - slinger as a threat to his new - found power and influence. He would fly around on his glider, throwing pumpkin bombs and causing chaos in the city.
In the Spider - Man franchise, the villain origin often has a strong connection to Peter Parker's personal life. Since Spider - Man is a more street - level superhero, his villains are usually from his own neighborhood or have a direct link to his daily activities. In contrast, in some other superhero universes, villains might be more global threats or otherworldly beings from the start. For example, in the Superman universe, a lot of the villains are powerful aliens right off the bat. In Spider - Man, it's more about the personal grudges and the city - level issues that lead to villainy.
Perhaps a new character, like a genetically - engineered super - soldier gone wrong. This villain could have super strength and agility similar to Spider - Man, but with a more aggressive and unpredictable nature. He might see Spider - Man as a rival and be determined to prove that he is the superior one in the city.