4. Mantis
Mantis is a half Vietnamese/half German superhero who has been on both the Avengers and the Guardians of the Galaxy teams. She's fought Thanos before and, alongside the Avengers and the Inhumans, she's fought Ultron at Quicksilver's wedding, of all places! Her powers are many with multiple mental powers like empathy, telepathy and precognition, to invulnerability allowing her to be exposed to space unprotected, and she's also an expert martial artist who's defeated Captain America and Thor separately. Throughout the character's history, she's had a thing for the Vision (who in this movie will be played by Paul Bettany aka the voice of Jarvis) and, seeing that Scarlet Witch, who's also in this movie, is the wife of the Vision, there might be a love triangle being set up between the three characters. Mantis is a little-known character but she's a visually striking and underrated one who's connected to a lot of the characters already confirmed to appear. But I wouldn't expect Disney to play up Mantis' past as a prostitute!