It adds drama. Fans like to see their favorite hero in difficult situations. When Spider Man is betrayed, it creates a lot of emotional turmoil and makes the story more engaging.
He would be very hurt. He might isolate himself for a while, doubting his own judgment in trusting his friends. Spider - Man might also start to question his identity as a hero. After all, if his friends can turn on him, what does that say about his relationships and his role in the world?
Even one of Spider - Man's fellow superhero friends might betray him. Maybe they get jealous of Spider - Man's popularity or feel that he is getting all the credit for their team's successes. This internal betrayal would add a lot of drama and conflict to the fanfiction story.
It's popular because it adds a new layer of drama. The war is over, but the problems don't end. It shows that even in victory, there can be backstabbing. People like to explore the darker side of human nature in the context of the Potter universe.
One example could be a story where Spider Man is betrayed by his friends in the Avengers. Maybe they suspect him of a crime he didn't commit due to some false evidence planted by a villain. Another could be a scenario where his love interest, like Mary Jane, betrays him by revealing his secret identity to the media out of jealousy or being manipulated.
It could be his mentor. In the fanfic, the mentor might think that Spider Man is becoming too powerful and is a threat to the balance of power. So, he could betray Spider Man by leaking his secret identity or setting him up to be captured by the authorities.
An anti - hero or a morally grey character might be the antagonist. This character could have a different view on relationships and superhero life. He convinces Spider Man that the harem is holding him back from achieving greater things. And Spider Man, being influenced, betrays the harem.
One possible plotline could be that Spider Man, perhaps due to some mind - control or misunderstanding, turns against the members of his harem. Maybe he starts working with a villain who convinces him that his relationships in the harem are a weakness. Another could be that he accidentally reveals secrets of the harem members, which they see as a betrayal.
In some betrayed Spider - Man fanfiction, it could be his love interest who betrays him. Maybe she's been manipulated by a villain into thinking Spider - Man is a threat. This can lead to a very complex and heart - wrenching storyline as Spider - Man tries to win her back and expose the true villain.
Venom is quite popular in Spider - Man fanfiction. His complex relationship with Spider - Man can be explored in many ways. He can be a villain, an anti - hero, or even an ally in some really creative fanfictions. Another popular one is Gwen Stacy. Fans love to write about her and Peter's relationship, especially in alternate timelines.
They're popular because it's a twist on the normal Harry Potter story. People like seeing the hero in a different situation, like being betrayed. It adds drama.