MJ would be heartbroken. She would try to be strong in front of Peter, but inside she'd be a mess. She might use their shared love of things like photography or theater to try and trigger his memory. She would also be very protective of him, not wanting any harm to come to him in his vulnerable state.
His friends would be very worried. For example, Ned would probably be constantly by his side, trying to find ways to help him remember. He might show Peter old photos or talk about their shared memories.
Peter will probably be very confused at first. He's used to being part of the team, and suddenly being hunted by them is a huge shock. He might try to talk to them to clear up any misunderstandings.
Peter would likely be defiant. He has a strong moral compass and wouldn't easily give in to Osborn's demands. He'd probably try to find a way to escape right away, using his spider - abilities like climbing walls and his super strength to break free from any restraints.
Peter would probably be scared at first. He's just a kid, after all, and being kidnapped by a powerful being like Thanos is terrifying. But he would also be defiant. He has a strong sense of responsibility, so he might try to find a way to escape on his own.
First, if the fanfiction is really good, you can recommend it to your friends who are also fans of Peter Parker. You can react by being critical too. If there are plot holes or if the character of Peter seems out of place, you can write a constructive review. Another way to react is by creating fanart inspired by the fanfiction. This shows your appreciation for the story in a creative way.
Their friends like Ned would probably be really excited at first. He might start making plans for the baby shower right away and offer all kinds of support, like helping them find a bigger apartment. As for Peter's aunt May, she would be overjoyed but also a bit worried. She would give MJ lots of advice on taking care of herself during the pregnancy.
Since Peter is Spider - Man, he has to be careful not to use his powers and reveal his identity. So he might just try to defend himself in a non - superhuman way, like using his quick reflexes to dodge Flash's blows as much as possible while trying to calm Flash down verbally.
Peter Parker's reaction was one of determination. He was motivated to do more to prevent such tragedies in the future and was driven to be a stronger hero. His emotions were a mix of grief and a resolve to make a difference.
One idea could be that Peter forgets his identity as Spider - Man. He starts to notice his strange abilities but has no idea where they come from. So he embarks on a journey to figure it out, all while his friends and family are trying to figure out what's wrong with him.
Some Avengers might be initially skeptical. Thor, for example, might not understand the power of a 'spider - boy' at first. But others like Captain America would probably see his potential and welcome him. Black Widow might be intrigued by his skills and try to train him further in espionage - related aspects.
Peter might be initially suspicious. After all, in his world, strange things often mean trouble. But then he could also be curious to find out more about this doppelganger. He might try to test the doppelganger's abilities, like seeing if they have the same spider - sense. If the doppelganger seems friendly, Peter could start to form a bond with them, sharing stories about their lives and learning from each other.