The Avengers would be furious. Natasha would use her spy skills to find out all about the bullies without them even knowing. Thor might be a bit more direct, perhaps showing up at the school in his full Asgardian glory to scare the bullies straight. Clint could offer to teach Peter some self - defense moves so he can stand up for himself.
Well, first of all, Bruce would be concerned not only about Peter's physical safety but also his mental state. He might offer to talk to Peter about how to deal with the emotional stress of being bullied. Wanda could use her powers to give the bullies a taste of their own medicine, not in a harmful way but just to make them understand what it feels like to be bullied. Vision, on the other hand, would analyze the situation from all angles and come up with a very logical plan to stop the bullying for good.
Well, when the Avengers find out that Peter is being bullied, it's a big deal. Bruce might use his scientific knowledge to create some sort of device that could detect when Peter is in a potentially bullying situation and alert the Avengers. Wanda could use her powers to give Peter some mental strength, like creating positive thoughts in his mind. Rhodey would be the practical one, making sure Peter has a proper support system at school. They all would come together as a family to make sure Peter feels safe and loved and not let the bullies get to him.
One way is by getting involved in Peter's school life in a more official capacity. Maybe they could arrange for some anti - bullying seminars at the school. Natasha could also train Peter in stealth and evasion techniques so that he can avoid the bullies more easily. Thor could even offer to be Peter's bodyguard for a while, at least until the bullying situation is resolved.
The Avengers might have a range of reactions. Tony Stark would probably be amused and might make some sarcastic comments about how the fanfiction portrays Peter. Steve Rogers would be a bit more confused at first, not fully understanding the concept but then find the positive portrayals of Peter endearing. Thor would likely think it's a strange Midgardian thing but be entertained by the stories that show Peter as a heroic figure.
Tony Stark would probably be both proud and a bit worried. Proud because Peter is this brilliant young mind who has managed to be a hero on his own, but worried because he's just a kid. He might start to hover over Peter more, offering him better tech and trying to mentor him more closely. Captain America would likely be very accepting. He sees the good in people and would be happy to have another brave soul on the team. He'd probably offer Peter some words of wisdom about using his powers responsibly. Thor might be a bit clueless at first. He doesn't quite understand the whole 'secret identity' thing as well as the others, but once he gets it, he'd be all for having Peter around. He might see Peter as a little warrior and be eager to train him in his own Asgardian ways.
Some Avengers might be protective. For instance, Captain America could immediately start giving Peter advice on how to better handle his dual identity and keep himself safe. He might offer training sessions to help Peter improve his skills as Spider - Man.
Well, in some fanfictions, if the Avengers find out about Peter, they might immediately take him under their wing. They could see his potential and start training him more intensively. For example, Tony Stark might give him access to even more advanced technology, and Captain America could teach him about strategy and leadership. It's all very exciting to think about.
Iron Man, on the other hand, might be more direct. He could use his technology to track Peter's actions and confront him. He might threaten to expose Peter's identity if he doesn't stop. And Thor would probably be angry at first. He values his fans a great deal and seeing Peter bully them would make him want to use his hammer to teach Peter a lesson, but then he would also try to understand the situation.
The Avengers might be initially shocked. For example, Iron Man could start by using his technology to find ways to help Hawkeye communicate better within the team. He might create special devices for him.
Peter might be really nervous at first. He's used to being just the friendly neighborhood Spider - Man, and now the Avengers know he's Tony's son. He could be worried about living up to their expectations.
The Avengers would react very strongly. Steve would be the first to offer moral support. He'd tell Peter that being bullied doesn't define him. Natasha would start investigating who the bullies are and their motives. And Vision, with his unique perspective, would try to help Peter see the situation from a different angle, to understand that the bullies are often the ones with insecurities. Meanwhile, Sam would be there to cheer Peter up with his friendly banter.