Across the Board: Achievement STEAM of Wolfenstein 2: The New Colossus

For this you must beat the story and use the enigma machine to track down and kill all Übercommanders. The enigma machine is a chair you can sit in, found in the hub area (Evas Hammer / Hammerfaust). It's in the same room where you select chapters for replay. You must find enigmas by killing & looting normal Commanders. Then use the enigma machine to decipher enigmas and reveal the locations of Übercommanders. The killboard can be found in the command center of the hub area. There you see pictures of who's dead or alive. One target is killed automatically at the end of the story.
Also see Where to Find Enigma Machine & How to decipher Enigmas.