Winter's Widow

When Yelena Belova found out about Natasha's sacrifice to save the world, her rage was almost uncontrollable. Desiring vengeance or at least an explanation, she traveled to New York to confront the remaining Avengers. What she found, however, in the form of Natasha's best friend - Agent Kasey Winter - was the ability to trust, open up, and even possibly love.

Best Rankings:
#1 - Yelena
#17 - Black Widow
#26 - Marvel fan fiction
#4 - Yelena Belova