Annihilus could be a likely villain. He is a powerful being from the Negative Zone. In the fanfiction, Annihilus could be drawn to Earth because of the energy signature created when the Avengers and Captain Marvel meet. He sees Earth as a prime target for conquest. His powerful cosmic control rod gives him an edge in battle. The Avengers and Captain Marvel have to quickly learn about his weaknesses and use their combined powers to stop him from destroying Earth and spreading his reign of terror across the universe.
Thanos could still be a likely villain. Even if he was defeated in the official storyline, in a fanfic he could return more powerful or with a new plan. His obsession with the Infinity Stones makes him a great overarching threat.
Iron Man and Batman might be the most likely to clash. Iron Man is all about high - tech and showing off his latest inventions. Batman, while also using technology, is more of a brooding, solitary figure. Iron Man might see Batman as a bit of a relic or too old - fashioned in his methods. Batman, in turn, could view Iron Man as a bit too flashy and irresponsible with his power. Their egos could get in the way of them working together initially.
In this fanfic, the main antagonist could be a scientist who has been corrupted by his own experiments. He creates some sort of energy - based monsters that are immune to normal attacks. Captain Marvel and the Avengers have to figure out how to stop these creatures and the mad scientist behind them.
Doctor Strange and Ajak. Doctor Strange is well - versed in the mystic arts and Ajak has a lot of knowledge about the Eternals' history and their connection to the Celestials. Their knowledge areas could intersect, and they would likely be the first to start sharing information. Maybe Strange senses some strange energy related to the Eternals and approaches Ajak to find out more.
Thor would be the most likely. Since Thor has a connection to Norse mythology already, he would be familiar with Sleipnir. He might see Sleipnir as a symbol of his home realm and would quickly bond with it. They could communicate in a way that the other Avengers can't, sharing stories of Asgard and the great battles there.
Iron Man would be a likely candidate. Tony Stark is known for his sense of humor and ability to tolerate eccentric personalities. He might see Deadpool's skills and be interested in using him for certain missions, while also enjoying the banter.
Well, I think Hulk and Hercules might become allies. They both are incredibly strong and simple - minded in some ways. They could have a friendly competition about who is stronger, but in the end, they would realize that they have a common ground in their brute strength. Another possible pair could be Iron Man and Hephaestus. Hephaestus is the god of blacksmithing and Iron Man is a technological genius. They could exchange knowledge about creating powerful weapons and armors.
I think it would be Spider - Man. Since he's also relatively young and has a sense of humor. He would be able to relate to Robin on a more personal level compared to the other Avengers. They could start chatting about their cool gadgets and how to use them in different situations.
I think Hamilton and Captain America would be likely to form an alliance. They both have strong beliefs in justice and freedom. Captain America fought for his country in a different time, and Hamilton was a key figure in the American Revolution. They could understand each other's values and work together towards some common goals, whether it's about protecting the people or promoting certain ideals.
It could be Captain America. He is often the one to reach out and try to make peace or form alliances. He would see the potential in the Maximoff twins and approach them with an open mind and a desire to work together for the greater good.