To uninstall Sophos your first point would be to see if you locate Remove Sophos Endpoint. This can be either run from launchpad or type it in spotlight. When you run that app it should then go away and uninstall the programme. It would be best to reboot the machine once the exercise is complete. I have found it does sometimes error out or fails but on a reboot this will tell you if you have managed to uninstall it. Help file link.
