Biggest “Happy Ending Override” in a sequel?

Basically when a sequel undoes most if not all of the happy ending(s) of the previous entry or entries

The very premise of God Eater 3 undoes all progress from the previous games. The Ash has turned the world into a far larger hellhole than it already was (which is saying a lot) to the point of the very air being toxic to non-God Eaters (and leaving the fates of the entire previous games cast uncertain). It’s also given rise to special Aragami called Ashborn, which are so incredibly powerful that before the protagonist’s team, no God Eaters had ever managed to kill one.

Speaking of God Eaters, in the previous games they were treated well, looked up to by the people and seen as heroes, to the point that they were actually paid more than their superiors. Now, they’re slaves at the mercy of their Ports and are viewed and treated as subhuman trash.