It happens. Some process runs away with the computer and you can't do anything. Here's how to log you or someone else out from a Mac from the command line.
Log into the computer with ssh. Open a terminal, and type ssh username@computername.whatever.edu . Note that if you are trying to log in to a Brandeis machine you may need to use the VPN to use ssh.
On the command line, type sudo launchctl bootout user/$(id -u <username>). Note that this step requires administrator access.
Notes:
This worked 2023-04-07 on a Mac running Ventura