The first female Avenger and a freelance S.H.I.E.L.D agent, Black Widow is one of the best characters of any gender in the MCU. Scarlett Johansson's first appearance in the role - in Iron Man 2 - was a little underwhelming, but the more we see of her, the better she gets. She has a pivotal role in both Avengers films and is an important part of the Captain America series, providing Cap with an equal (if more ruthless) partner. Black Widow's backstory is pretty dark, taken at a young age and trained by the KGB to become an extremely deadly assassin. Her defection to America and subsequent heroics with the other Avengers have done little to assuage her guilt, making her a refreshingly complex hero. Just please, please Marvel - drop the ludicrous Hulk-romantic-storyline and let her get back to kicking and shooting in the next film. What's your favourite female character in the MCU? Have your say in the comments down below.