Sure, you can spend all your time in Prey trying to save the world and all the people on Talos 1. But maybe, instead, don’t do that? Killing everyone, it turns out, is also an option. Pursuing this path will eventually get you the "Showing Initiative" optional objective, when Walther Dahl arrives on the station. But you’re going to have to do a little work before he gets there.
Dahl and the "Showing Initiative" objective require you to kill a bunch of people. However, Prey’s "I and It" achievement/trophy requires that you "Kill every human on and around Talos 1," as its description says. That’s 42 people.
So how do you do it? The short version is: Shoot everyone. There’s a little bit of nuance to it, though. In this guide, we’ll show you how to find and kill them all to become a psychopath.
How to find and kill everyone
You need to kill mind-controlled humans attached to typhon telepaths. These kills won’t count if their heads explode when you get to close to them or when you kill the telepath. This applies to the quarantined patient in the Trauma Center in the Talos 1 Lobby, the survivors in the Greenhouse in the Arboretum and the humans wandering around the Crew Quarters in the Dining Room and Fitness Center.
You’ll also have to ignore (or seek out and kill) people asking for help, like Dr. Igwe during "Doctor Igwe" and Mikhaila in "Assist Mikhaila Ilyushin." Later, you’ll have to purposefully do "Escape Attempt" out of order to destroy the escape pod.
When you get into the Cargo Bay during "Shipping and Receiving," you can kill Sarah Elazar and her security officers. You can loot Sarah’s body for the keycard you need — which circumvents the requirements of "Shipping and Receiving" and "Cargo Bay Defenses."
Alex will still put up with you through your murder spree and the events of "The Keys to the Kingdom" and "Before I Give You The Key" will unfold normally. You’ll still have to scan the typhon coral for him, and Dahl will arrive when you upload the data.
In this version, though, Dahl likes your bloodthirstiness. He’ll propose that you help him out, since he’s under orders to kill everyone, and you’ve done most of his work for him already. You’ll get the "Showing Initiative" optional objective, which will add four more station crew members to your hit list. Hunt them down — they’re all in Life Support — and kill them to complete the objective.
After you’re done, and you go to collect your reward from Dahl, you can shoot him, too.
Alex will still come out of hiding. When you go to meet him, you can shoot him, too. Make sure to loot his corpse for the Arming Key and Prototype Nullwave Transmitter fabrication plan. Now you can finish the game with whichever ending you prefer. Your final review is going to be pretty uncomfortable, though.