We Own The Night Achievement & Trophy
In Mission 13: Going Dark, when you have to use a rope to repel down to a large open town area, there will be three marked main objectives. They are the Church, Clocktower, and Pool. You must kill all enemies in these three locations without them starting to shoot at you to get the “We Own The Night” achievement. Just kill everyone you see, and carefully go through the entire building. Also, increase the volume of your game so you can hear enemies talking or making other noises (using headphones helps to hear where the sounds are coming from). Since the enemies are roaming around and do not always stay in fixed places, it will slightly vary where they are. You will get the achievement as soon as you cleared out all enemies in those three locations. You do not have to complete the mission to unlock it. The big building in the middle where they hold Hadir can be ignored. If you get spotted, you can restart the checkpoint. Enemies are allowed to find corpses, but they cannot start shooting at you. The following is the number of enemies at each place and their locations:
Clocktower: There are 10 enemies. Kill the two upstairs and the one at the barricaded back exit behind the building. The other seven are either inside or roaming in the yard or street.
Church: There are 13 enemies. There are four on the left side, three on the right side, four inside, and two roaming the general area, often around the left side of the church but they can take a while to appear. On some playthroughs they were there when arriving at the church, but other times they only appeared after killing the other 11 enemies.
Pool: There are 12 enemies. There are two at the fuse box behind the building, three inside the pool where the hostage is, one in the garden behind/below the pool house, and six outside/on roof/roaming the area.