How do I disable WebEx Assistant on startup for Mac?
Try System Prefs > User &amp; Groups > Your name > Login Items.

Select it in the list &amp; click the - button underneath

If it's not listed there, then check either /Library/LaunchDaemons/ or /Library/StartupItems/ to see whether it has an entry in there.
It's safe to remove items from there - though they will continue running until the next reboot.  

If you want to be able to restore functionality in future, zip the file in situ then trash the original.