The command-line to uninstall Avast Endpoint Protection from the system is:
cmd /c "C:\Program Files\AVAST Software\Avast Business\Setup\setup.ovr" /uninstall /cleanall /verysilent /reboot 30
Note: The uninstallation requires a reboot to delete the Avast Antivirus services and unload its' associated kernel and file-system drivers from the working system.