Nebula shouldn’t have been the one wielding the Infinity Gauntlet, and if Nebula had killed Thanos in Avengers: Endgame
Writers for Avengers: Endgame recently revealed that Nebula nearly wore the Infinity Gauntlet in the blockbuster at Marvel Studios, but the scene was removed from the script in the early stages because they felt it undermined the climax of Tony Stark. Despite his explanation, the way this series of events unfolds is not entirely in line with proper storytelling techniques and he feels too forced to be ultimately satisfying.
It is clear that the writers worked backward in designing the last two Avengers movies. They knew it had to end with Tony Stark’s sacrifice because he was the character who launched the Marvel Cinematic Universe and because Robert Downey Jr.’s contract had ended and they had to get him out of the movies. It seems they were writing towards a destination and allowing the plot to dictate the character, rather than allowing the characters to lead the plot. Doing the latter would have led them to the inevitable conclusion that it should have been Nebula who wielded the Infinity Gauntlet to defeat Thanos.
While Thanos has been around early UCM since his mid-credits appearance in The Avengers, he had no real connection to the Tony character’s journey. Nebula and Gamora were the characters that really had a direct relationship with Thanos. Nebula was a lackey to Thanos in Guardians of the Galaxy, but his character evolved further in Guardians of the Galaxy Vol. 2 as the public learned more about his fight with his abusive father. She deserved the opportunity to complete her story arc and be the one to finally end Thanos’ reign of terror.