The entire movie could've ended early if not for Star-Lord.
My guess is that you've seen Avengers: Infinity War by now. If not, minor spoilers are ahead.
Anybody who has seen Marvel's superhero masterpiece can relate to the feeling of disappointment whenever Star-Lord's name comes up. Iron-Man, Spiderman, Doctor Strange, and most of the Guardians of the Galaxy had Thanos pinned down on his home planet. Mantis used her abilities to put Thanos to sleep while the rest of the crew worked at removing the Infinity Gauntlet from his hand. While the plan was working smoothly, Star-Lord got caught up in his feelings when he finds out that Thanos killed Gamora, the Mad Titan's daughter and Star-Lord's girlfriend. Just when the Infinity Gauntlet was slipping off, Star-Lord disrupts the process and accidentally frees Thanos, which leads down a path of ultimate destruction.
Infinity War directors Joe and Anthony Russo sat down with HuffPost, and admitted that fans shouldn't be so hard on Star-Lord. “His mother was dying of cancer when he was kidnapped by pirates at the age of 10. He was raised by pirates. He had to murder his father to avenge the death of his mother. His girlfriend, who he was in love with, was murdered by another corrupt paternal figure ... He made a very emotional choice,” explained Joe Russo. His brother continued on to claim that if fans are mad at Star-Lord, they should be equally annoyed with Thor.
“Thor also let his emotions get the better of him. Thor could’ve killed Thanos more quickly than he tried to with the ax. He showed up, and he took a moment — because of his anger, because of his motivation — to tell Thanos that he told him he would die ... and finish him off in a very deliberate way. Thor sort of got lost in his emotions in a similar way as Star-Lord and could also have been responsible for Thanos," Anthony stated.