I looked through the achievements today and noticed Overpowered:
Overpowered
Beat a mission on Commander+ with a squad composed entirely of soldiers of the same class (but not Rookie)
In my second game on WotC (which was on Commander), I remember completing the Codex Brain Coordinates mission with only a single high-ranking ranger, but I didn't get this achievement. Since it was only one soldier, would I have gotten the achievement had I taken 3-5 additional rangers?
Best Answer
Yep, that's correct. You need to fill up the squad (whatever is your current maximum squad size) with soldiers of the same class.
This thread claims you can get the achievement during a War of the Chosen covert op, thus only requiring 2 soldiers.