Despite fighting on the same side in “Avengers: Infinity War,” Black Widow and Mantis never joined together on-screen. Black Widow fought side by side with Captain America, while Mantis joined her fellow Guardians of the Galaxy crew in taking the Infinity Gauntlet away from Thanos.
MCU femme fatales Black Widow and Gamora fighting together would have been awesome, but both died tragically to save the world. Black Widow sacrificed herself in Hawkeye’s place, while Gamora was sacrificed by Thanos.
In “Avengers: Infinity War,” Black Widow and Drax were fighting two different battles on two different planets, and Drax died by Thanos’ snap. Although Drax came back to life, Natasha was killed off for good.
In “Avengers: Infinity War,” the Guardians split up, and Star-Lord and his crew were swiftly snapped by Thanos on another planet, while Natasha was earthbound in another battle. Star-Lord never got the chance to battle it out on earth with the heroes, including Natasha.
Hope van Dyne first suited up as the wondrous Wasp in "Ant-Man and the Wasp," but she was unfortunately among the casualties when Thanos snapped half of the universe out of existence. Sadly, one hero that Hope didn't get to meet was Black Widow, as it was the latter's death that made it possible for the former to be resurrected.