Here's Where Black Widow Ended Up In The What If...? Season Finale
A place for everything and everything in its place. At the conclusion of the Season 1 finale of "What If...?" there's a home for every single member of the Guardians of the Multiverse, the team assembled from across time and space to defeat the ultimate version of Ultron. For some, that means returning to the worlds that The Watcher plucked them from after a hard-fought battle. For others, it means finding a new home to call your own.
To quickly recap, in Episode 9, "What If... The Watcher Broke His Oath?", Black Widow uses one of Hawkeye's arrows containing the Arnim Zola virus and stabs Ultron in the eye with it as the Guardians of the Multiverse battle the villain. The move works but gives way to Erik Killmonger and the Zola-infected Ultron to fight for possession of the Infinity Stones while Strange Supreme, the superpowered Doctor Strange variant, and The Watcher are around. For the time being, that means Zola/Ultron and Killmonger are stuck inside a pocket dimension, and that dimension is trapped inside a slightly larger pocket dimension Strange Supreme inhabits.
While the remaining members of the Guardians of the Multiverse return to their own universes, The Watcher still has to deal with one remaining (and accidental) member of the team, Black Widow. She refuses to go back to her world after Ultron wipes it out in Episode 8. Instead, The Watcher takes her to a universe where a Black Widow is desperately needed, but where is that?
The Watcher places Black Widow in a world where she is needed
After everyone else from the Guardians of the Multiverse returns to their respective worlds at the end of "What If...?" Episode 9, The Watcher allows Natasha Romanoff, aka Black Widow, to find a new home. She didn't have much of a world to return to after Ultron destroyed hers in Episode 8. So, The Watcher breaks his oath to never intervene and helps this Black Widow variant find another place to settle down.
The Watcher transports Black Widow to a world where Captain America, Captain Marvel, and Nick Fury battle Loki and the Chitauri on the Helicarrier. The all-seeing character drops Black Widow right into the action and tells her that, in this world, Black Widow is dead. Seeing the opportunity help, our multiverse Widow launches a sneak attack against Loki, steals his scepter, and seemingly brings the fight to a swift conclusion. We're never given an official explanation on the location of this new world, but there is a specific statement that reveals which universe Black Widow arrives in — and it's one we've seen before. In Episode 3, "What If... The World Lost Its Mightiest Heroes?", Hank Pym wipes out most of the would-be Avengers as part of a revenge plot before Nick Fury can assemble them. The only surviving Avengers are Captain America and Captain Marvel, dubbed the "replacement Avengers."
In the "What If...?" season finale, we hear the team we see in those final moments referred to as the "replacement Avengers," too.We can't say for certain this is the world Black Widow winds up in just yet, but all the pieces seem to fit perfectly. Perhaps we'll find out definitively when "What If...?" returns for Season 2.