Styx: Shards of Darkness

Unfortunately, there is no way in this game to simply knock an enemy unconscious. Any confrontation with an enemy results in their death. For this insignia you must complete an entire mission (all zones) without killing anyone. The PS4 pause menu will tell you at any time how you are progressing with this insignia. You begin every mission with it satisfied and it will instantly update if you kill anyone so check it before every Quick Save to ensure you're still good. This will unlock during the mission completion screen.

Note: Story-related kills do not count against the trophy.

See Oh My Gob! for videos of a mercy run through every mission.