Well, if we consider the character dynamics, Peter is often seen as the younger, more idealistic hero compared to Tony. So, if Peter dies instead of Tony, it would completely change the trajectory of the story. Tony, who has been through a lot already, might be pushed to the edge. He could either become more withdrawn or more determined to avenge Peter. And the other characters like May, Ned, and the rest of the Avengers would be deeply affected. May would be heartbroken, Ned would lose his best friend, and the Avengers would have to face the reality that they couldn't protect one of their youngest members.
One possible scenario in such a fanfiction could be that Peter, in a self - sacrificing move, takes on a powerful enemy that was originally meant to target Tony. Maybe Peter's inexperience and pure heart lead him to misjudge the danger, and he ends up giving his life to save others, while Tony is left to grapple with the guilt.
In this type of fanfiction, the death of Peter instead of Tony might be used to explore different themes. For example, it could show the impact of a young hero's death on the rest of the superhero community. Peter's death could shatter the hopes and ideals that he represented, and Tony might be forced to re - evaluate his role as a mentor and a hero. It could also lead to a darker and more complex storyline where the characters have to deal with the loss in different ways.
The story could focus on Tony's downward spiral into guilt and self - blame. He might isolate himself from the other Avengers, feeling that he should have been the one to die. His technological advancements could take a dark turn as he tries to find a way to bring Peter back, perhaps even dabbling in dangerous and unethical science.
One possible plot development could be that Peter is left with a huge sense of guilt. He might struggle with survivor's guilt, constantly thinking that it should have been him. He could then become overly reckless in his superhero activities, trying to prove that he was worthy of being saved. Another aspect could be how the other Avengers deal with Tony's death. They may turn to Peter as a symbol of hope, since Tony sacrificed himself for Peter. This added pressure on Peter could lead to him either rising to the occasion or crumbling under it.
Peter's character arc would take a very dark turn. He'd likely be consumed by grief and a sense of obligation. His once - carefree and enthusiastic approach to being a superhero would be replaced with a more solemn and determined one. He might become more secretive, not wanting to let others in on his pain.
In a fanfiction sense, Tony might kidnap Peter due to a misunderstanding. For example, if Peter was involved in some sort of experiment that Tony misinterprets as dangerous. He could be worried that Peter is being influenced by the wrong people or powers, so he kidnaps him to figure out what's really going on. Tony's actions, although extreme, could be driven by his love and concern for Peter as a mentor.
Well, clearly Peter Parker and Tony Stark are the main characters. Peter is the one who 'snaps' in this scenario, which means he has a significant character shift from his normal self. Tony, on the other hand, serves as a sort of contrast or the catalyst for Peter's snapping. Even though Peter is the one with the new behavior, Tony's presence and actions are likely to be integral to the story as they are what cause Peter to snap.
In this fanfiction, it could be that Peter snaps after Tony makes a decision that Peter strongly disagrees with. Let's say Tony decides to sacrifice a certain group of people to save the majority in a moral dilemma. Peter, who has a stronger sense of justice for the individual, snaps and decides to go against Tony's plan. He then has to fight not only the external threat but also deal with the rift he has created within the team.
The 'tony is dusted instead of peter fanfiction' could have a very interesting plot. Since Tony is such a central and resource - rich character, his sudden dusting would be a huge shock. Pepper would be devastated. Peter, on the other hand, would be in a difficult position. He might try to use his own powers and intelligence to figure out a way to bring Tony back. The other Avengers would be looking to him for leadership in some ways, as he was the one closest to Tony among the younger heroes. And the whole dynamic of the post - 'dusted' world would be completely different from what we saw in the movies, with new alliances and strategies being formed in the absence of Tony.
You can try looking on some popular fanfiction websites like Archive of Our Own (AO3). It has a vast collection of fanfictions, and there's a good chance you might find it there.
Perhaps in this fanfiction, Tony Stark has lost his mind a bit. He could be under the influence of some sort of alien technology or a powerful spell that makes him see Peter as a threat. This could lead to him kidnapping Peter in order to neutralize what he perceives as a danger. But as the story progresses, he might start to come to his senses and realize his mistake.
Perhaps Peter is a bit annoyed at first. He's trying to focus on class and here's Tony calling. But then when he realizes it might be something important, he starts to pay more attention to the call, all while being cautious not to get caught by the teacher.