They show him kindness and try to understand his motives. They offer support and help him find a better path.
Thor's relationship with Loki would likely become more complex. He'd be glad his brother is being cared for but also worried about Loki's true intentions. The Avengers, like Tony, might start to see Loki as more than just a villain. They could develop a begrudging respect for his intelligence. For Loki, he might start to feel a sense of belonging, which is something he's never really had. This could soften his attitude towards the Avengers.
One possible plot could be that the Avengers find a weakened Loki after a battle. They decide to take care of him not out of trust but to keep an eye on him. Thor is conflicted as he wants to believe his brother can change. They nurse Loki back to health, and during this time, Loki starts to see the Avengers in a different light, leading to some comical and heart - warming moments as he tries to fit in without losing his mischievous charm.
In fanfics, the Avengers can take care of Peter in many ways. They could share their own experiences with him. Thor could talk about his battles and how he overcame difficulties, which would inspire Peter. They can also help him with his identity as a superhero. Maybe Doctor Strange uses his magic to show Peter different versions of himself and how to choose the right path. And of course, they can just be there for him as friends, having movie nights or sharing meals together.
If Loki impersonated Thor, the real Thor would be furious when he found out. The other Avengers, like Iron Man, might initially be confused but then quickly realize something is off. Iron Man would likely use his technology to detect the impostor. Hulk might just smash first and ask questions later when he senses something wrong with 'Thor'.
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.
Well, Thor might be a bit shocked at first. He'd probably be amused by some of the wilder interpretations of his brother in the fanfiction. Captain America, on the other hand, would likely be confused by the whole concept as it's so different from the traditional stories he's used to. Iron Man would probably make sarcastic comments about how creative the fans are in coming up with these stories.
In some fanfictions, Loki might use his magic to outwit the enemies that the Avengers are facing. For example, he could create illusions to deceive the villains and lead them into a trap.
Loki could also provide the Avengers with valuable information about otherworldly threats. Since he has connections to different realms, he may know about an upcoming invasion. In return for his help, he could demand that the Avengers clear his name for some of his past misdeeds, leading to an interesting dynamic between them in the fanfiction.
In fanfiction, the Avengers might learn about Loki's hidden motives. For example, some fanfictions depict Loki having a more complex backstory regarding his actions in the MCU. He could be revealed to have been acting out of a sense of misunderstood loyalty or a desire for acceptance that was misdirected.
One reason could be that they see Loki as a victim of circumstances. Maybe they've come to understand that his actions were often influenced by forces beyond his control, like Thanos' manipulations. So they decide to defend him in Asgard.