Once it is installed and configured, there are two ways to start it:
Using the brew services start tor command
Using the tor command
In the former case, I can always stop it using the brew services stop tor command. But how to stop it in the latter case, given that I already closed the current terminal session, and therefore Control-C won’t help?
So killall tor or killall -9 tor should force your tor to stop.
If you have multiple instances running you can check with ps -jef or ps -jef | grep tor which are running and then use kill $PID or kill -9 $PID where $PID matches your process you want to end.