I'm not entirely sure why you would want to do ?
What is it that you are trying to achieve ?
As it seems to go against what avast antivirus is designed to do, protect your system.
If it was indeed possible to do this, then surely any piece of malware could do the same.
Avast and no doubt other antivirus programs will try to protect against simple command line commands to uninstall the protection. Avast also has a self-defence mechanism to protect avast files/folders, etc. etc.
The clean uninstall utility if run in windows normal mode, it would require to restart the system in safe mode and then do its uninstallation.