Attack on Titan 2

Super simple, just play the scouting missions and this will eventually unlock as it's technically story related in a sense. Just make sure you have decent gear and you'll be fine. For this specific achievement you don't have to go after Dire Subjugations or S ranks as you just have to finish the mission.

I highly recommend waiting to finish the main campaign before going on these missions as you'll have your character more built. Playing with other people is a viable option; however, these can all be done solo so don't be upset if you don't have anyone to play with.

Once you've done 1/4 of the Scouting Missions this achievement will unlock. I'll go more in depth on what you should be looking for as a character and whatnot in the solution for Survey Merit 3 for getting 100% Scout Missions done.

You can get this by just completing the normal scout missions. I advice you doing the survey missions with other people because it will go way faster.