There could be a villain who is a shape - shifter. This villain can transform into anyone and uses this ability to deceive suction cup man and his friends. The shape - shifter might also have some sort of anti - suction technology or just be really slippery so that suction cup man can't get a grip on him. He wants to take over the city and suction cup man has to stop him. The villain could also be spreading lies about suction cup man to turn the public against him. This would make it harder for suction cup man to do his job of protecting the city. There are so many ways this shape - shifter villain could cause trouble for suction cup man.
A mad scientist who creates a device that cancels out suction cup man's powers could be a great villain. He could be jealous of suction cup man's abilities and wants to prove that his science is superior.
A plot idea could be that suction cup man is part of a secret society of people with strange powers. His suction cup ability is initially seen as a joke by the others, but he ends up being the key to solving a mystery that threatens the society. He might also use his suction cups to communicate with some sort of underwater creatures that can only be reached by adhering to the walls of their underwater lair. Additionally, he could be in a world where gravity is changing constantly, and his suction cups are the only way he can move around safely.
Venom is also a strong candidate. In this fanfiction, he could be more powerful than ever. He might be infected with some sort of alien symbiote that gives him enhanced abilities. Venom could target Spider - Man because he wants to prove that he is the stronger one. And by attacking Spider - Man, he also draws the attention of the Avengers, which he sees as a challenge. He could start by attacking the city and luring Spider - Man and the Avengers into a trap.
The Green Goblin could be a great main villain in a crossover. Imagine if he teams up with Doctor Doom from the Fantastic Four universe. Their combined evil intelligence and power would be a huge threat to Spider - Man and whoever he teams up with in the crossover.
It could be Doctor Doom. He might be seeking to take over multiple universes in a crossover. Spider Man stands in his way, and Doom, with his superior intellect and powerful magic, manages to defeat Spider Man. His death would then be a huge shock to other heroes in the crossover, like the Avengers or the Fantastic Four who then have to avenge him.
It could be Obadiah Stane's son or protege. He blames Iron Man for his mentor's downfall and decides to target Iron Man's daughter to get revenge. He uses his own resources and knowledge of Stane's old technology to create chaos and try to harm the girl.
Loki could be a great main villain. He could trick Spider - Man into believing that Thor is a threat to Earth and set them against each other. Then, while they are fighting, Loki could carry out his real plan which might involve stealing a powerful artifact from both Asgard and Earth.
Lex Luthor could be the main villain. He's a classic Superman foe and always has some devious plans to take down Superman.
It could be a new trainer who has just started their journey. They are eager to prove themselves in the Wallace Cup.
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.
A tech - genius who was once a protégé of Tony Stark but turned against him out of jealousy. He creates his own army of robotic suits.