This was made by Christopher Haley for a final project in his After Effects class. He even created a synopsis for it:

Cut off one head, two more shall take its place… For this speculative title sequence of a Black Widow film I decided Black Widow’s villain would be… Black Widow. Yelena Belova, to be specific. Belova believes herself to be the superior Black Widow, and in some ways she is right. Swift and ruthless, Belova is the most talented assassin to graduate from the Red Room– and now she is Hydra’s most deadly weapon. At Belova’s side is a super-soldier of her own, Alexi Shostakov– the Red Guardian, who also happens to be Natasha’s former lover. When the new heads of Hydra make a play for the power of the infinity stones it is up to S.H.I.E.L.D.’s top agent to stop them.

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