Black Widow (Natasha Romanoff)
Her First appearance is in Iron Man 2 (2010). Trained from a young age by the KGB under the code name Black Widow, Natasha's top-notch assassin skills placed her on S.H.I.E.L.D.'s hit list. Marked for death, Hawkeye instead spared Natasha's life, convincing her to take up a new job in America. There she was tasked to infiltrate Stark Industries and gauge whether Tony and his Iron suit would be up for joining the Avengers initiative. After the team assembled, she thwarted Loki's Chitauri (alien) invasion, pulled apart Ultron's robotic army, and assisted Captain America in taking down The Winter Soldier (partly as revenge for his shooting her in the stomach). An attempted romance between she and Bruce Banner (The Hulk) was...a little awkward, so since then it's been all about training new Avengers War Machine, Falcon, Vision, and Scarlet Witch.
Played by: Scarlett Johansson
Universally known as one of the sexiest women in Hollywood, Scarlett Johansson has actually been acting professionally since the age of eight. A native of New York City, where she was born on November 22, 1984, Johansson was raised -- along with her twin brother -- as the youngest of four children, and she developed an interest in acting at the age of three. After enrolling in classes at the Lee Strasberg Theatre Institute for Young People, she made her stage debut opposite Ethan Hawke in the off-Broadway production of Sophistry. Her film debut followed in 1994, when she had a supporting role in North, and she subsequently appeared in the little-seen Just Cause (1995) and If Lucy Fell (1996).