In such a fanfiction, perhaps the Avengers could be shocked by how much Peter has grown and developed in the future. He might show off new powers or skills he's acquired. For example, his Spider - Sense could be even more advanced, allowing him to predict complex threats far in advance. And he could offer new perspectives on old foes the Avengers have faced, based on his future experiences.
Hulk could be the most surprised. He doesn't always pay attention to the subtleties of character growth. But seeing Peter, who was once a small and somewhat inexperienced hero, now be this confident and powerful figure from the future would really catch him off - guard. He might even be a bit intimidated at first by the new - found strength and presence of future Peter.
The Avengers might react in different ways. Steve Rogers would probably be polite but firm in getting to know Peter's boyfriend. He'd want to ensure that he was a good influence on Peter. Thor, on the other hand, might be a bit more boisterous. He could either be really friendly and enthusiastic, or his loud and powerful presence might accidentally scare the boyfriend a bit.
Since he might be related to Tony Stark, there could be an emotional connection for the other Avengers. They might feel a sense of obligation to protect him or guide him, which changes their group dynamic. For example, Captain America might take on a more father - figure role towards Peter. Also, his presence could create some jealousy or competition among the Avengers who want to be his mentor or closest ally.
I think Thor could be really excited too. Thor loves a good warrior and Peter, with his spider - like abilities, would be an interesting addition to his view of heroes. Thor might be amused by Peter's small - scale heroics compared to his own grand battles and would enjoy seeing Peter's potential grow.
In such a fanfiction, Peter could show off his unique skills to the Avengers. Maybe he'd surprise them with his agility and quick thinking. For example, in a battle scenario, he could use his web - slinging abilities to outmaneuver enemies that the Avengers are having trouble with.
Future Loki might interact with the Avengers in a cautious way. He knows their past opinions of him and tries to prove himself. He could start by sharing small bits of useful information. For example, he might tell Iron Man about a weakness in a new enemy's technology.
Obviously, Peter (presumably Peter Parker, Spider - Man) would be one of the main characters. And of course, the Avengers members like Iron Man, Captain America, Thor, Hulk, Black Widow, and Hawkeye are likely to be main characters too as they are the ones 'meeting' Peter.
In such a fanfiction, the Rogue Avengers might initially be suspicious of Peter. They could test his loyalty and skills. Maybe Peter has to prove himself worthy to join their cause against the establishment Avengers. For example, he could show off his spider - powers in a unique way that impresses them.
One scenario could be that the Avengers are facing a new threat that requires Peter's special skills. His ability to stick to walls and his enhanced strength could be crucial. Peter might also introduce a sense of youthful enthusiasm to the group. He could crack jokes during tense situations, which at first annoys some of the Avengers but later they come to appreciate it as a way to lighten the mood.