XCOM 2

Tested on Jan. 13/14th, 2023

Even tho the Multiplayer has been removed, it is still possible to achieve it through the pre-21.10-support - support branch.

Activate the beta branch, start the game and hop into Multiplayer Ranked match with your partner, and just kill each other.

Not sure how long this will last, better do it now than later.

Edit: I noticed that some people are still having trouble unlocking it via this method. As far as I know, this achievement used to be buggy, even in the vanilla version (experienced it first hand). What I could tell you to try, if the problem persist, is to verify the integrity of the game files before looking for a match. (Right click X-COM 2> Properties > Local Files > Verify the integrity of the game files).

That's only thing I could come up with, as it fixed my problem after trying like 4 times and no achievement, at the time (before the MP removal). Other people say it unlock after losing against your friend, another, that only the host gets it, I'm not really sure but it is better to try more alternatives. Also, starting the game with the DLC expansion (War of the Chosen) could also help.

If nothing, then emulating another OS could solve it (since MP has not been removed on Mac/Linux), even tho is a pain. (I haven't test this one, don't take my word for granted).

Mods and configs could prevent you from unlocking this achievement, so beware.

Tested on Jan. 13/14th, 2023

Even tho the Multiplayer has been removed, it is still possible to achieve it through the pre-21.10-support - support branch.

Activate the beta branch, start the game and hop into Multiplayer Ranked match with your partner, and just kill each other.

Not sure how long this will last, better do it now than later.