5. Sif
Aside from Frigga, Sif is the only female Asgardian we've truly met in the MCU. She's also the only one who seems to be able to give Thor a run for his money. She's the leader of the motley Sif and the Warriors Three and, as admitted by Thor, she is the one who "proved wrong all who scoffed at the idea that a young maiden could be one of the fiercest warriors this realm has ever known." Cool! Evidently, Asgard follows the patronising view of young women as maidens who must be protected by their hyper-masculine male counterparts. Sif ain't got time for that. She nearly takes down the Destroyer single-handedly in Thor and when she is injured, she declares: "I will die a warrior's death! Stories will be told of this day!" Sif is afraid of nothing. Furthermore, she is the first - and often only - Asgardian to confront Loki about his banished brother and she recognizes Loki's jealousy for what it is. Did any of the Warriors Three blatantly tell Heimdall that they would commit treason to rescue Thor? Only Sif is unafraid and determined to do the rescuing, even if it means breaking Thor's heart by revealing that Loki had lied about Odin's death. And anytime a so-called young maiden has to rescue a giant Viking of a man who got banished because of his foolish pride, I'm on board.