According to this
https://xcom.fandom.com/wiki/Commander
Twice
The Commander does not take to the field personally in most scenarios,
only being seen on the field twice, the first during the Tutorial, and
the second during the final mission, where they psionically control an
Avatar to lead the final combat mission of XCOM 2, Operation
Leviathan.
Of course, the commander is ourselves. I do not remember seeing the commander in the tutorial and final mission.
Where is it?
Any screenshot?
Best Answer
You have this screenshot right on the wiki page you linked showing the Commander before the final mission.
You see the commander in a similar suit during the rescue mission Operation Gatecrasher. It's intended for the person to be obscured by the suit to allow your imagination to fill in whoever you like, as the Commander is your personal avatar in the game.
Note, that you only see the Commander in XCOM 2, not XCOM: Enemy Unknown.