Canon: "Marvel's Agent Carter" (Marvel Cinematic Universe/Earth-19999) (Dottie was performed by Bridget Regan)
Bio: "Dottie Underwood" (real name unknown) is an early product of the USSR's Red Room program, having graduated during World War II. Originally serving the Soviet scientific agency Leviathan, Dottie was cut loose by the Soviets after her handler, Viktor Fenhoff, subverted a Leviathan mission to steal Howard Stark's war technology in order to enact a personal revenge plot against Howard. He failed to do so due to the heroic efforts of SSR Agent Peggy Carter. Dottie escaped to try to survive on her own, alone, in the United States. About a year later, she was captured by Peggy Carter while trying to steal an object belonging to the mysterious Arena Club from a bank. Oddly enough, Peggy herself freed Dottie from Federal prison when she needed assistance investigating that very same Arena Club. Dottie stole a sample of "zero matter" (a.k.a. Darkforce) from supergenius Whitney Frost but was then captured (she dropped the sample for Peggy's associate Jarvis to find, so she did complete her mission). She was tortured by Frost--the zero matter causing severe pain and distress to even the jaded and nearly fearless Dottie--before being rescued/recaptured by Peggy. Dottie escaped Peggy again when Peggy was distracted by an emergency trip to the hospital. She is now again on the run, no country or organization to support her.
Notable Abilities: As a graduate of the Red Room, Dottie has skills typical to the assassins who will eventually come to be known as "Black Widows": exceptional agility, acrobatic capabilities, hand to hand combat skills, marksmanship, disguise, languages, cold reading, and considerable snark. If she builds up enough momentum via her acrobatics, she can snap a man's neck with her bare hands, and safely fall from great heights if she has enough wall to kip off of on her way down. Though the MCU has never confirmed if the Black Widows have relatively minor supernatural enhancements like their Marvel-616 counterparts, she does seem to recover from injury slightly faster than normal (but it's hard to tell whether that's an enhancement or TV magic).