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.
His relationship with Black Widow could also be affected. Black Widow has a long history with Shield. Spider Man might view her with distrust, which could lead to some interesting and conflict - filled interactions in the fanfiction. He may not be as willing to team up with her as he would be in the normal Marvel universe.
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.
Power struggles can be a reason. Spider Man, being a solo hero with his own set of powers and moral code, might not agree with Shield's more bureaucratic and sometimes secretive ways of handling things, so they clash. For example, Shield might want to control Spider Man's actions, which he resists. This can lead to a fight. Also, there could be a villain manipulating events behind the scenes to make it seem like Spider Man is against Shield or vice versa.
One common plotline is betrayal. Maybe his team betrays him for some gain, like siding with a powerful villain in exchange for something they desire. This makes Spider - Man feel angry and hateful towards them. Another is the team being too self - centered. They focus only on their own goals and achievements, leaving Spider - Man feeling left out and resentful.
Spider - Man himself is obviously a very popular character. His acrobatic fighting style and quick - witted personality make him a fan favorite. Then there's Agent Coulson, who is often seen as a mentor figure. His calm and collected nature in the face of danger is really appealing.
There's a fanfiction called 'Spider - Shield Rivalry' where Spider Man is wrongly accused by Shield of a crime he didn't commit. This sets off a chain of events that results in some amazing fight sequences. It also delves into the moral dilemmas of both sides.
Another way is through character relationships. A Shield agent might be initially skeptical of Spider - Man, seeing him as an unregulated vigilante. But as they work together, they come to respect and trust each other. This evolution of their relationship can be a central theme in the fanfiction, with their combined efforts against villains being a by - product of their growing bond.
One great example could be a story where Spider - Man teams up with a Shield agent to take on a new supervillain in New York. The agent might provide high - tech gadgets and intel to Spider - Man, while Spider - Man uses his superpowers to get them out of tight spots during the mission.
One interesting plot idea could be a crossover where Spider - Man has to team up with the Agents of Shield to stop a new super - villain who has the ability to control technology across the globe. This would force Spider - Man to use his street - level skills along with the high - tech resources of the Agents of Shield.