Yelena Belova

Yelena entered the franchise as a correction to it — a Widow who found the whole business of heroic posing ridiculous, and said so. That comic register has survived every subsequent appearance, which is unusual for a character who is also grieving a sister through most of them.

She comes into Doomsday from the Thunderbolts side of the ledger rather than the Avengers one, and the film has to reconcile a team of people who were, until recently, assets rather than heroes.

Her skill set is entirely human and entirely lethal, which puts her in the same structural position as Sam Wilson: no powers, in a fight against people who have them.