1. Avengers: Endgame
Avengers: Endgame being No. 1 is going to make some Black Widow fans mad, but it’s such an important movie. Natasha Romanoff makes the ultimate sacrifice, and ultimately, it saves everyone. Without her, they never beat Thanos.
Following the events of Infinity War, Black Widow is one of the few remaining Avengers after the Blip. She teams with Iron Man, Captain America, Hawkeye, Hulk, Thor, and the rest of the gang to go back in time to stop Thanos from acquiring the Infinity Stones.
While she needed some help from the rest of the Avengers to finish the job, Natasha sacrifices herself so Clint Barton/Hawkeye can get the Soul Stone to make sure that Thanos will never be able to sacrifice Gamora and acquire the Soul Stone the way it happened during Avengers: Infinity War.
One of the main criticisms of the movie was how it treated Romanoff’s death and how it was overshadowed by Tony’s sacrifice, funeral, and send-off, but I don’t necessarily agree. We saw both of these stars Robert Downey Jr. and Scarlet Johansson basically join the MCU together. RDJ starred in Iron Man while Johansson starred alongside him in Iron Man 2. And, Avengers: Endgame brought their stories to a close, although we got to see a whole new side of Natasha Romanoff in Black Widow, which was released two years after Endgame.
As mentioned, we get to see Romanoff’s impact during the Black Widow post-credits scene. It wasn’t the same as Tony’s, but it was unique and it was hers.