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.
Hawkeye could also be a candidate. He has an affinity for animals, as seen with his friendship with Lucky. He might be the first one to approach Sleipnir in a non - threatening way, offering it food or just trying to calm it down. Through this initial kindness, a bond could form between them, and Hawkeye could learn to ride Sleipnir, adding a new dimension to his skills in battle.
Strange could be the one. With his knowledge of magic, he would be intrigued by Sleipnir's magical nature. He might study Sleipnir to understand the connection between Norse magic and the magic he uses. In the process, they could form a bond as Strange protects Sleipnir from those who would misuse its power, and Sleipnir in turn could help Strange access new sources of magic.
One possible plot could be that Sleipnir, the eight - legged horse from Norse mythology, somehow ends up in the Marvel universe. The Avengers initially mistake it for a threat. But then they discover that Sleipnir is being chased by some dark Norse entities. The Avengers decide to protect Sleipnir and in the process, they learn about Norse magic and mythology, and how it can be both a help and a hindrance in their own universe.
Thor could be the main character. Since he has a connection to Norse mythology and Sleipnir is from that realm. He would be the one most likely to understand Sleipnir and communicate with it.
One possible plot could be that the Avengers are on a mission in a realm where they accidentally stumble upon Sleipnir. They initially mistake it for a threat but then realize it has its own intelligence and might be an ally. Maybe Sleipnir can help them travel through different dimensions to stop a greater evil that is spreading across the multiverse.
Iron Man could also be a likely candidate. Tony Stark is known for his charm and his ability to work with all kinds of people. He might be intrigued by Flash Thompson's bravado and see it as a starting point to shape him into a better person. He could offer Flash some cool tech gadgets and in the process, form a friendship. Stark would likely use his wit and intelligence to get through to Flash and show him a different way of looking at things.
I think it would be Spider - Man. He's closer to her age in a way compared to the other Avengers. He can understand her more easily, like the things she likes, the new trends, etc. And he has that friendly neighborhood hero vibe that would make the girl feel comfortable around him quickly.
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.
Not really. Sleipnir is more associated with Norse mythology and doesn't have a prominent presence in Marvel Comics.
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.
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.
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.