You find Waltz, who it turns out is Mia’s dad and Aiden’s father figure. He starts a process of launching rockets to destroy the city or something, I can’t remember and it doesn’t really matter. After you do a boss fight with him, a very frail and maybe dying Mia walks out of a door and says “stop fighting guys,” and suddenly you and Waltz are besties. Y’all are like “oh shit, the rockets are gonna destroy the city but we’re friends now!” You have to choose between letting your actual bestie Lawan sacrifice herself to blow up the rockets in the bunker, or save her and let the rockets launch, destroying the city.
Side note, remember Hakon? That fucker that betrayed you and then tried to kill you like three times? If you didn’t murder his ass the first chance you got, he comes in for a heel-face turn and blows up the rockets himself, saving Lawan and the city. That’s an ending I just found out about, because on my playthrough I spent a few extra grenades making sure his dumb Judas ass was actually dead.
You might be wondering, what happens to Mia after the ordeal with the rockets? Good question! The game literally goes from “save the city and let Lawan die or destroy the city and let Lawan live” to Aiden fucking off into the wilderness. I was so goddamn pissed when I found out that the WHOLE REASON AIDEN CAME TO THE CITY was left as a loose end. Maybe the DLC ties it up. I’m certainly never gonna find out.