Ace Killer Achievement in Valkyria Chronicles 4
Defeated 15 enemy aces.
How to unlock Ace Killer
There are 51 total aces in the game, and only one per map if one is present at all. You may need to go out of your way to find some of them, as they won't always be in the direct path of the mission. Check the PSNProfiles guide to find their locations (he provides maps of every mission and they are marked by the same stylized "A" you get when you A-Rank a mission). You only need 15 for this achievement, but all of them drop unique weapons or tank parts which are needed for other achievements, so be sure to kill them all eventually. It may be a smart idea to write down which ones you've killed as you go.