If you tuned in to the latest episode of What If...?, you already know who was determined to get rid of the Avengers. But who killed Hank Pym's daughter and caused the scientist enough grief to go on a murderous rampage? A key detail in Episode 3 may have confirmed that Black Widow knew who that secret assassin was and had previously survived a deadly attack.
What If ...? Episode 3 takes place in the past before the Avengers were formed. In the episode, the members were still being recruited by Nick Fury but for some reason, they all end up being killed right before their recruitment.
It is ultimately revealed that Pym had become Yellowjacket and he is seeking revenge for the death of Hope Van Dyne. In Pym's opinion, his daughter was Fury's fault because she was killed while she was on a mission as a SHIELD agent.
So who killed Hope in the first place? It has been pointed out that she was killed somewhere in Odessa, Ukraine. It just happens to be the same location where Natasha Romanoff first encountered the Winter Soldier.
In Captain America: The Winter Soldier, Nat tells Steve Rogers about her encounter with the legendary assassin where Bucky Barnes had shot out her tires near Odessa. Although Nat doesn't confirm whether she is the only one on that mission, it is possible that Hope was with her or, in this reality, was the nuclear engineer that Nat was trying to protect.
It's important to note that in The Winter Soldier, Nat's engineer was male. However, What If...? brings us to a different reality so it is possible that it was Hope who was in the car with Black Widow.
The next episode of What If...? will air on Wednesday, September 1, 2021.