Quicksilver could be one. In the movies, he didn't get as much screen time as he could have. In a multiverse fanfiction, he could be from a universe where his powers are even more enhanced and he plays a crucial role in a team - up. Another is Mockingbird. She has great combat skills and intelligence but isn't as well - known in the Avengers context. In a multiverse story, she could be a key figure in a different reality's Avengers.
Moon Knight. He's a complex and interesting character. In an 'Avengers Multiverse Fanfiction', he could be from a universe where his dissociative identity disorder gives him unique powers related to each identity. And there's Sersi from the Eternals. Since the Eternals are connected to the larger Marvel cosmos, she could be a powerful and underrated addition to an Avengers multiverse story, perhaps bringing knowledge of other multiverse secrets.
One underrated character is Black Widow. She has a wealth of spy skills and martial arts expertise. In Avengers Battleground fanfiction, she could be the one to gather intelligence on the enemies before the battle, and then use her combat skills to take out key targets during the fight. Another character is Quicksilver. His super - speed could be a game - changer on the Battleground. He could run circles around the enemies, delivering quick blows or stealing important items. And Bucky Barnes, the Winter Soldier, with his enhanced strength and combat training, could have some great storylines. Maybe he has to face off against some of his old enemies from his time as the Winter Soldier on the Battleground.
One underrated character is Agent Coulson. In another dimension, he could have some latent superpowers that are activated, and he becomes a key player in helping the Avengers. Another is Mockingbird. She has great combat skills and could be shown in a dimension where she has to lead the Avengers in a situation where the usual leaders are incapacitated. And then there's Sif. In a different dimension, she could bring some unique Asgardian knowledge and abilities that are crucial for the Avengers' survival.
Some characters might be in awe. For instance, Thor could be excited to see different versions of himself and his friends. He might see a version of himself that is even more powerful or a version of Loki that is actually good, and it would be a shock but also a source of amusement for him.
Agent Madani is also somewhat underrated. Fanfiction could show more of her backstory and how she really feels about working in a world full of crime and violence. She could be given more complex relationships with other characters, not just Frank. For example, her interactions with other law enforcement agents or even some of the criminals she has to deal with.
Definitely the core Avengers like Iron Man, Captain America, Thor etc. Since it's about the multiverse colliding, we'll probably see their alternate versions too. For instance, a more steampunk - inspired Iron Man from a different universe or a female Captain America.
One underrated character is Kamala Khan. She has such a unique power set and personality, but often doesn't get as much focus as the more well - known Avengers. Another is Taskmaster. His skills and the mystery surrounding his character can be explored more in fanfiction. Also, Black Widow sometimes doesn't get enough spotlight considering her complex backstory and skills in the game.
Huntress could be a great choice. She has her own sense of justice and skills that could add an interesting dynamic to the Knightfall story. Another one is Azrael. He has a complex backstory and his presence during Knightfall could be explored more deeply.
One underrated character is Robbie Robertson. He could be featured more in fanfiction. He has a connection to the Daily Bugle and could be involved in a story where he discovers some secret about Spider - Man and has to decide whether to expose it or help protect him. It could add an interesting layer of moral dilemma.
Moaning Myrtle. She's central to the Chamber of Secrets story, but there's more that could be done with her. In fanfiction, she could have a more complex personality. Maybe she has some secrets of her own about the Chamber, or she could form an unexpected friendship with one of the main characters, which would change the dynamic of the story.
Thor is often a very popular character in 'Avengers Multiverse Fanfic'. The idea of different Thors from different universes, with different levels of power and different personalities, is really appealing. For example, there could be a Thor who has lost his hammer but gained an even more powerful weapon. Loki is also popular. His trickster nature can be even more complex and interesting when exploring the multiverse, as there could be versions of him with different motives and alliances.