One great Avengers protect Loki fanfiction is 'Loki's Redemption'. In this story, the Avengers realize Loki has been misjudged. They see that his actions were often a result of being manipulated. Thor takes the lead in protecting his brother from other threats, while Iron Man uses his tech to keep Loki safe from various Asgardian and earthly enemies. It's a really interesting take on the characters.
The fanfiction can also be about redemption. Loki getting protected by the Avengers can be the start of his journey to make up for his past wrongs. It gives hope that even the 'villains' can be redeemed and find a place among the heroes, and this theme is always interesting in the world of superhero stories.
If 'this' is a superpower, it can be used directly to defend the Avengers. For instance, if it's a power of invisibility, the holder can use it to spy on the enemies and prevent surprise attacks on the Avengers.
Thor would be a likely candidate. Since he is Loki's brother, he already has a connection with him. Thor might be the one to convince the other Avengers to give Loki a chance and be the first to reach out and try to befriend him in this new situation.
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.
In many fanfictions, the Avengers protect Hawkeye by using their unique powers. For example, Thor might use his lightning to fend off enemies approaching Hawkeye. Captain America would use his shield to block attacks aimed at Hawkeye. And Black Widow could use her combat skills and stealth to take out threats before they reach him.
In this fanfiction, Loki might interact most with Hulk. It would be an interesting dynamic as Loki is a master of manipulation and Hulk is, well, the Hulk. Loki could either try to use Hulk for his own purposes, which would be very dangerous, or he could end up on the wrong side of Hulk's anger. But at the same time, it could also lead to some unexpected moments of understanding or at least a begrudging respect between them.
He would probably interact a lot with Thor. Since they are brothers, there is a pre - existing relationship full of complexity. Also, he might interact with Iron Man quite often. Tony Stark's sarcastic nature and Loki's trickery could lead to some really interesting exchanges, either in the form of verbal sparring or working together on some high - tech and magic - combined projects.
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.