Sasuke could fit in as a stealth and combat expert. His ability to move silently and strike quickly would be valuable. He could also use his sharingan to analyze threats and come up with strategies.
In fanfiction, he could fit in through his values. Superman has a strong sense of justice and morality, which would align well with the Avengers' goals. He could also form friendships with the members, like a bromance with Thor due to their similar god - like statuses.
Well, Will Solace could potentially be a healer in the Avengers fanfiction. His skills in treating the wounded could be really useful. He could patch up the Avengers after their battles, much like how he does in his original series. Maybe he'd be a bit out of place at first with all the high - tech and super - powered stuff going on, but his kind heart and medical expertise would soon make him an important part of the team.
He could use his invisibility cloak for stealth missions with the Avengers.
Percy could fit in as a strategist. His experience in dealing with various gods and monsters gives him a unique perspective on handling threats. He might suggest different approaches that the Avengers haven't thought of before, like using the environment in a more creative way, similar to how he uses water in his battles as a demigod.
Magnus could fit in as a sort of magical consultant. His knowledge of Norse magic and the Nine Worlds could be invaluable when the Avengers face threats with a magical origin. For example, if they encounter a dark sorcerer from the Norse realms, Magnus would know how to counter their spells.
One way Desmond Miles could fit into the Avengers universe in fanfiction is through his Assassin's Creed skills. He could be a covert operative, using his stealth and combat abilities to assist the Avengers on secret missions. For example, infiltrating enemy bases undetected.
Harry could fit in by using his magic for reconnaissance. His invisibility cloak would be great for spying on enemies unnoticed. The Avengers could use this to their advantage when planning attacks.
They could fit in by using their skills. Nico's combat abilities and Will's support skills would be useful. For instance, Nico could fight villains directly while Will helps from the sidelines.
In fanfiction, the Punisher's entry into the Avengers is often a bumpy ride. His methods are so different from the Avengers'. He might start as an adversary to some of the Avengers who don't approve of his killing ways. But as the story progresses, he could prove his worth. He can offer a different perspective on combat and strategy. He might be the one to take on the dirtiest jobs that the more 'heroic' Avengers are reluctant to do. This creates an interesting dynamic within the team, as they have to balance his presence with their own moral code.
Poseidon would bring a whole new set of powers and a different kind of leadership style to the Avengers. His control over the seas and water - based powers could be used in various ways, like creating barriers or using water to put out fires during battles. In terms of dynamics, he could be a bit of a wildcard. He might not always follow the Avengers' rules, but his intentions would be good. For example, he might decide to take on a powerful enemy alone, thinking he can handle it, which could cause some tension within the team.