So far, there's several heroes which we know for sure will be in the game. There's a number of the heavy-hitters from the movies: Thor, Captain America, Iron Man, The Hulk, and Black Widow.
There's also a new hero: Ms Marvel
— otherwise known as Kamala Khan — who was revealed
a few months ago. She's not been in the movies, but she does have her own comic series. She first appeared in Captain Marvel #14 in 2013, and then moved onto her own series from February 2014. She'll be integral to the story. She's a huge Avengers fan, and was there on A-Day, when they fell apart. Kamala was exposed to the Terrigen Mist that day, and is now showing signs of her own polymorphic and healing powers. Being such a fan of the Avengers is her drive, and that of the story as well, because it's this that pushes her to set out to reunite the Avengers team and prove their innocence.
It seems this aim will dictate how the player will interact with each Avengers hero. We know that we'll get to play extensively with each, through their own specific story missions; but it seems that it's Kamala's determination to root them out of hiding which gives us this individual access. Each hero will have their own unique story, as well as their own gameplay styles. Thor will have his hammer Mjolnir, Hulk will have his raw, rage-fuelled power, Captain America will have his shield, Iron Man will have his extensive technology, and Black Widow will have her agile reflexes and stealth equipment. They'll also have their own Heroic moves, intrinsic ability, combo systems, and move sets.
As for villains, we only know about a couple. We've faced off against Taskmaster
in our preview of the game's A-Day prologue, and we know that in the months following A-Day the city has been partially rebuilt by A.I.M.
, a nefarious technology-driven company that has continually plotted world domination in the comics since the 60s.
Square Enix's comment about the story continuing after the game has launched, and new heroes being added, suggests that it won't be long before there's more heroes to choose from in the game. It's not yet clear whether these will be familiar faces from the movies or comics, or relatively newer heroes like Kamala.