XCOM 2

Your first Retaliation mission will come at the end of the first month, and others will appear every five weeks (or sooner, if they are part of a Dark Event). If you fail or ignore a Retaliation mission, then you will lose contact with the region that mission was in so it's not advised.

In these missions, your objective is to save civilians. Really, your objective is to minimize causalities. Civilians will die, usually on the first turn, with you being completely unable to do anything about it. Civilians are spread out across the map and enemies will happily pick one or two off each turn. Civilians die in one hit. In order to "save" a civilian, you must move one of your soldiers into range of the civilian (indicated by a glowing blue circle). The civilian will then realize a war zone is a bad place to stand and they will flee the map. Until then, they will remain in place, although they might run to another location if they get spooked by enemy movements.

You need to save at least 6 civilians to successfully complete a Retaliation mission. For this trophy, however, you can only allow up to three civilians to die. There is a lot of luck in that because sometimes you simply can't reach them in time. To make matters worse, some civilians are actually the Faceless, which are hideous monsters disguised to look like humans (similar to the Thin Men in Enemy Unknown). The Faceless won't reveal themselves until you approach but they can be nasty to deal with, as they have a long-reaching swipe attack and a decent amount of health. They often reveal themselves and move/attack on the same turn, which is rather cheap. To unlock this trophy:

1. Just accept that some Retaliation missions make it impossible to get this trophy. You will have other chances later on.
2. Notice the placement of the Faceless remains the same on the map, even if you reload an earlier save. If you want, you could make a manual save at the beginning of the mission, learn which civilians are real and which are the Faceless, then reload the earlier save and plan out your strategy accordingly.

It should also be noted that enemies would prefer to kill you over civilians. Given the opportunity, ADVENT troops will almost always target your soldiers first so you should spread out your troops. The more ground you cover, the more civilians you can save, and the more likely you are to "trigger" an enemy pod that will begin concentrating its attacks on you. Rangers are great for Retaliation missions because they have high mobility and can absolutely slaughter the Faceless up close with a shotgun or blade.