The Agent Carter TV series may not have gotten quite as many viewers as the mainline Avengers films, but it introduced us to our first Black Widow other than Natasha: an assassin who went by the name of Dottie Underwood and infiltrated Peggy Carter's boarding house as an operative of the shady Leviathan organisation. Through Dottie's story, we learn more about the decades of horrors inflicted by the Red Room, including a particularly nightmarish training scenario that requires two assassins-in-training to fight to the death in front of everyone. By the end of the series, Dottie and Peggy had briefly become reluctant allies against a common enemy, only for Dottie to escape after their mission, leaving her ultimate fate unknown.