Even though she was left for dead by her own people, she manages to survive the Zerg and eventually learns to control them. Despite how many times Jim Reynor goes out of his way to save her from the Zerg's grasp, Kerrigan inevitably causes chaos wherever she goes.
She struggles between her humanity and her evil ambitions to take over the universe. She has so much depth -- and in defiance of all adversity, always comes back. Which is why I ranked her number 1.
Do you agree? Disagree? Have any other female antagonists I left out? Comment below!