Captain Marvel is often considered one of the most powerful Avengers. Her powers include energy absorption and manipulation, flight, and superhuman strength and durability.
Thor is often considered one of the most powerful Avengers. His godly powers, like his hammer Mjolnir and his ability to control lightning, give him a significant edge.
I think Omnimon and Thor would be a very powerful combination. Omnimon has incredible strength and a wide range of attacks, and when combined with Thor's godly powers and his mighty hammer, they would be almost unstoppable. They could take on the biggest threats both in the Digital World and in the Marvel universe.
Thor would be a strong contender. His god - like strength and the power of Mjolnir, or Stormbreaker, could be very effective against the Titans. He could fly in and smash the Titans with his hammer, and his lightning powers could also do significant damage.
Tony Stark and Steve Rogers are a very popular pair. Their contrasting personalities, with Stark being the brash playboy inventor and Rogers the moral - centered soldier, make for great body - swap scenarios. Another popular pair is Thor and Loki. Their complex relationship as brothers adds a lot of depth to body - swap stories. And Hulk and Bruce Banner also feature often. The duality of the man and the monster in one body is an interesting concept to play with in a body - swap setting.
The arc that involves time travel in the Avenger graphic novel is quite engaging. It allows for different versions of characters to interact and changes the course of events in unexpected ways.
Loki is often a popular character in Avenger OC fanfic. Many writers create OCs that interact with Loki in various ways, whether it's as an ally, a love interest, or an enemy. His complex personality and backstory provide a lot of material for interesting stories.
Iron Man is often a popular character in avenger time travel fanfic. His intelligence and technological prowess make him a key player in any time - travel scenarios. He can figure out the mechanics of time travel devices and come up with strategies to fix problems in the timeline.
I think Thor would be the most interesting. If he turned into a large and powerful animal like a dragon, he could breathe fire and fly. His already - impressive strength and combat skills would be enhanced, and he could be a real force to be reckoned with. He could also use his dragon form to intimidate enemies and protect Asgard or Earth in a very different way.