Who she is: Hela
Her power: Hela is the Asgardian goddess of death, so in addition to the usual Asgardian abilities of superhuman strength, speed, and so on, she also historically has mystical abilities over life and death.
Played by: Cate Blanchett
Where will we see her next? She makes her Marvel debut in Thor: Ragnarok, coming November 3, 2017.