Avengers: Endgame wasn't too kind to Peter Quill or at least the version from the branched timeline.
The plan of the remaining heroes was to go back to the past and retrieve the Infinity Stones. War Machine and Nebula were tasked to beat Star-Lord to stealing the Power Stone in Morag and they did so by knocking him out cold.
Screen Rant points out that this causes Star-Lord the small window he had to get the Power Stone before Korath does. This would mean that Ronan the Accuser successfully gets his hands on the "orb" and destroy Xandar with no Guardians to stop him.
The site explains that the Avengers: Endgame time travel basically undoes the events of the Guardians of the Galaxy. It was the fact that he got in the way of Thanos that he met the girl he loves and the family he always longed for.
Additionally, it was Gamora who helped him accept the death of his mother. Rocket was the one who found the gift she had for Quill before she passed. He wouldn't learn the truth about himself and his evil planet of a father if it wasn't for his newfound friends.
Even though Captain America brought the Power Stone back to its original place in time by the end of Avengers: Endgame, the time travel intervention still triggers a series of events far different from what we see in the Guardians of the Galaxy films.
Star-Lord is essentially left without family and friends and will be nowhere be as happy as he became with the Guardians by his side. Maybe after he came to, he returned to the Ravagers and may have devised another way to get the Power Stone, but it might have been too late.
This is definitely quite a dark punishment for his slip-up in Avengers: Infinity War. Even then, fans learned to forgive him because he was the reason we got a new movie. Thankfully, the fate of the original Star-Lord in Avengers: Endgame is much better. The Gamora he knew is gone, but she's still somewhere in space. She may not share the same feelings and memories with Quill, but she knows they have a special connection, which we might likely see in the next Guardians of the Galaxy film.
For more articles like this, take a look at our Avengers: Endgame page.