To uninstall Avast from your system you need to uninstall it using the avast clear utility tool.
• First of all, you need to download the tool on your desktop.
• After downloading you need to start your windows in safe mode then run the file.
• Choose the folder which contains the Avast software and click on ‘remove’.
This should help you uninstall the program from your system. But if this fails you need to contact How to contact Avast customer service
to get the help from a verified technician or an employee.