James Gunn, director of the Guardians of the Galaxy movies, helped screenwriters Christopher Markus and Stephen McFeely on Avengers: Infinity War, and he had one issue in particular that he wanted them to change.
According to the writing duo, Gunn, who was also an executive producer on the film, wanted to write dialogue for the space-faring team to make sure that their characterizations remained consistent with their own movies. As Gunn has been the only director to handle them so far (and will apparently stay that way, as he is currently working on their third and presumably last movie), one senses that he is a bit protective of them.
The two talked about working with Gunn in an interview with Backstory Magazine. They also revealed one key part of the movie that Gunn insisted on (and warning: spoilers to follow!)
“The only change he really went deep on and we had more than one conversation about was the decision by Star-Lord to shoot Gamora,” McFeely explained.
In the movie, Thanos (Josh Brolin) is trying to collect the six Infinity Stones, which will give him the power to destroy half of all life in the universe; his adoptive daughter Gamora (Zoe Saldana), a member of the Guardians, knows where the Soul Stone is located. She makes Peter Quill/Star-Lord (Chris Pratt) promise that if Thanos tries to capture her, he’ll kill her, so that the location of the Stone will die with her.
Apparently, Markus and McFeely felt that Star-Lord should find himself unable to do it, or even outright refuse. Gunn explained that no, Star-Lord should actually try to do it, an opinion which Pratt apparently backed up.
“It’s not a traditional hero arc,” McFeely said. “We were trying to get to a failure because his love for her outweighed his duty in some ways. And Gunn and Pratt were really adamant that he would do it.”
So Star-Lord took the shot, but for the plot to work, it had to fail―Thanos used the Reality Stone to turn his bullets into harmless bubbles. But the fact that he tried made a dramatic moment, and most fans agree that the moments where he and Gamora made this agreement were some of their best interactions in the film. His struggle helps make up for some of his less-than-stellar other moments in the film.