Maybe in the fanfiction, the return of the Avengers is due to a new, even more powerful threat emerging. This could lead to them reuniting despite past differences and grudges. They would have to quickly figure out how to work together again to face this new enemy.
In some 'Return of the Avengers fanfiction', the return could be a result of time - travel shenanigans. An Avenger from the past or future might show up, changing the course of events for the current Avengers. This could bring about a whole new set of challenges and adventures as they try to understand and deal with this unexpected arrival.
One interesting plotline could be the return of a long - lost Avenger who has been in hiding or captivity. For example, they might come back with new powers or a different perspective, causing a shift in the team dynamics.
One interesting plotline could be a civilian who is caught in the middle of a battle and is saved by the Avengers in a very unexpected way, like being teleported to safety by Doctor Strange at the last second.
One interesting plotline could be Wolverine having to team up with the Avengers to stop a powerful mutant - created virus that threatens to wipe out both mutants and non - mutants alike. He brings his unique combat skills and healing factor to the table, while the Avengers contribute their various superpowers and high - tech resources.
Another plotline might involve Loki getting caught in a time - loop within an Avengers - related adventure. He keeps reliving the same day, and each time he has to interact with the Avengers in different ways to try and break the loop. This could lead to some really comical and also tense situations as he tries to figure out what's going on while the Avengers are getting increasingly suspicious of his behavior.
Another plotline might involve Merlin coming back to find Camelot in chaos. His return then becomes a journey of restoring order, not just through his magic but also by reuniting the people and rebuilding their trust in the kingdom. He might have to deal with those who have misused power in his absence.
Maybe an Avenger grows to a giant size and has to fight off an equally large enemy. This could involve them using their newfound size to their advantage, like picking up cars and using them as weapons, but also having to be careful not to cause too much destruction in the city.
One possible plotline could be Yelena initially being distrustful of the Avengers. Maybe she has been taught to view them as enemies, but as she gets to know them, she realizes they have similar goals. For example, she might find common ground with Natasha's former teammates in their fight against evil.
Perhaps a plotline where the Avengers from different universes have different moral compasses. Some might be more ruthless in their methods of dealing with the multiverse collision. This could lead to internal conflicts within the newly - formed multiverse Avengers team. They would have to figure out how to work together despite their differences while also trying to save all the universes involved.
One interesting plotline could be the reader having a special power that the Avengers initially don't understand. For example, the reader might be able to control time in small bursts. The Avengers, being protective, try to help the reader master this power without it getting out of control. Another plotline could be the reader coming from a difficult background, like being an orphan in a war - torn area. The Avengers adopt the reader and show them a new life filled with hope and family. It could also be that the reader has some sort of connection to an enemy the Avengers are facing, and they have to figure out how to deal with that while still protecting the reader.
One possible plotline could be about an Avenger who was thought to be dead rising from the ashes, literally or metaphorically. Maybe they come back with new powers or a changed perspective, and they have to find their place within the team again.
She could be a super - spy too, but on a different side initially. Maybe she was brainwashed by a shadowy organization. Natasha then has to fight her sister while also trying to bring her back to her senses. It would be a story full of action and emotional turmoil.