It looks like The Last of Us Part 2 may have had a much darker tone during earlier drafts of the script, all the way to a completely different theme and ending. This shouldn't come as much a surprise, seeing as how the game has a number of deleted scenes and involved plenty of redesigns before the final product shipped.
In an interview with Game Informer, Creative Director Neil Druckmann and Narrative Lead Halley Gross both commented on the process that led to building The Last of Us Part 2's story and the ending. Of course, considering how much this new discussion comments on the overall story and the game's ending, there will be Major Story Spoilers to follow.
The current ending of The Last of Us 2 involves Ellie having the chance to finally kill Abby, holding her underwater and about to drown her, but holds back as a way of both giving up on her vengeance and allowing her to save Lev. However, according to Gross and Druckmann, Ellie's sudden change of heart was not always meant to be the case, with Abby originally dying and Lev being left helpless in his boat. While there may be secrets in the current ending, this alteration completely changes the way that the game expresses its themes and the ultimate development of Ellie's character.
This alternate ending was abandoned once the narrative team had decided that Lev should survive the events of the game, which incidentally meant that Abby would have to survive as well. As a result, the current ending does include hints at Lev and Abby's happier fate and manages to preserve some of the humanity that many players worried would be lost in Ellie's character. As Druckmann and Gross put it, while this ending changes the original themes quite a bit, maintaining the better parts of Ellie from the first game was likely worth altering course to keep Abby alive.
Naughty Dog's stellar writing in the original The Last of Us, and while The Last of Us Part 2 has been fairly decisive for a number of reasons, players have still found plenty to love and hate about the game, especially the characters. So making these changes to the ending to leave Abby alive and allow Ellie to retain her humanity, will likely prove to be a major boon to the series if the developer decides to explore either of these characters further.
The Last of Us Part 2 is available now on PS4.
Source: Game Informer