In the fanfiction, it could be that Spider Man has a personal vendetta against one of the Avengers members. For example, if one of them had a past with a villain that Spider Man has a strong connection to, like if an Avenger unknowingly helped the villain in the past, Spider Man might transfer his hatred for that villain to the Avenger and by extension, the whole team.
One possible reason could be a conflict in ideologies. Spider Man might believe in a more individualistic approach to justice, while Shield's methods could seem too bureaucratic or controlling to him.
One reason could be a misunderstanding. Maybe some events were misinterpreted, and the Avengers thought Spider - Man was involved in something bad. For example, if there were some crimes that seemed to have Spider - Man's fingerprints all over them, but in reality, he was being framed.
It could be due to a mind - control device. Some evil force might be controlling the Avengers and forcing them to torture Spider - Man. This would add an element of helplessness to the story as the Avengers are not acting of their own free will. Another reason might be a deep - seated jealousy within the Avengers. Perhaps they feel that Spider - Man is getting too much attention and they want to put him in his place, which is a very dark and out - of - character take but possible in the realm of fanfiction.
Another possibility is that the Avengers are being manipulated by a villain. The bad guy could be using false information to make the Avengers believe that Spider - Man is a danger. So they go after him without really knowing the truth.
In the 'Spider Man Becomes Toxin Fanfiction', it could be that Spider Man is tricked into wearing a piece of alien technology that is actually a Toxin - like symbiote in disguise. The symbiote slowly takes over his body and mind, turning him into Toxin. Additionally, the fanfiction might explore the idea that Spider Man's own self - doubt and internal struggles somehow attract the Toxin - like transformation. He may be feeling inadequate or guilty about something, and this negative energy makes him a prime target for the Toxin transformation.
One possible reason could be a misunderstanding. Maybe Spider - Man is framed for a crime he didn't commit, and the Avengers, being the protectors of the world, believe the false evidence against him. For example, a powerful villain could have planted evidence to make it seem like Spider - Man was involved in a large - scale attack on a city. Another reason could be a difference in ideology. If Spider - Man starts to take actions that the Avengers think are too extreme or irresponsible in his fight against crime in New York, they might decide to hunt him down to stop him from causing more potential harm.
One possible reason could be a difference in ideology. Maybe Spider - Man has a more local - friendly approach to crime - fighting while the Avengers are often involved in large - scale, global threats. He might feel that his skills are better utilized in his own neighborhood, like Queens, rather than in the grand, often cosmos - level battles of the Avengers.
The plot might involve Spider - Man getting into some trouble in New York and the three Avengers coming to his aid. It could be that a powerful alien artifact has been stolen and Spider - Man accidentally gets blamed for it. The Avengers then step in to help clear his name and find the real culprit while also protecting the city from the potential danger of the artifact.
In a fanfic, Spider - Man could be injured while on a mission with the Avengers in outer space. Maybe they are exploring an alien planet and are attacked by some sort of bio - mechanical creatures. Spider - Man is separated from the group and gets severely injured by one of the creatures' acidic attacks. His injury makes it difficult for him to use his powers effectively, and the Avengers have to find a way to both get him back to Earth and find a cure for his injury.
Spider - Man would likely be confused at first. He respects the Avengers and can't understand why they are suddenly after him. He might try to talk to them, to explain that he's innocent. For example, he could swing up to Captain America and start pleading his case.