Unlike heroes like Steve Rogers, who flirts with worthiness and eventually achieves it, Natasha Romanoff spends her time redeeming her past crimes and unjust actions through her superhero exploits.
It’s worth pointing out that she’s well aware of her internal condition throughout this process and hardly needs validation. When something as petty as lifting Mjolnir is literally put on the table, she laughs it off as something she doesn’t need to confirm. Likely, she already knows she’s unworthy — and she doesn’t care.
This display of intellectual strength and ethical awareness is powerful. Unlike everyone else in the Avengers, Romanoff doesn’t need to judge herself via a magic hammer that an insecure alien prince (with plenty of blood on his own hands) is touting as a detector of worthiness. She is on her own journey — one that ultimately leads to her own pure, personal sacrifice to save half of the living creatures in the universe.
It’s worth pointing out that this is a cinematic story arc, not a comic book one. She does try to lift the hammer (though in a much more desperate moment) in the comics — and sure enough, she succeeds. Of course, that sort of development would take a story like “Age of Ultron” in a very different direction. It appears Kevin Feige and Company opted instead for a casual, self-aware dismissal, saving the reveal of Romanoff’s worthiness for the future and creating one of the most powerful moments in the MCU in the process.
