There seems to be no obvious way or easily accessible guide on how to force logout / kick another user on MacOS.
Force quitting / killing loginwindow process seems to leave many processes still running.
The only command that seems to completely kill off all processes owned by the user is:
sudo launchctl bootout user/uid
Do note that the launchctl bootout subservice takes the specifier for the user in the numeric format.
To get the numeric format of a specific user with the username john, use:
$ id -u john
503
As such, to force logout john, you should:
sudo launchctl bootout user/503
Hope this helps! :)