After using Avast Clear on a Win 10 PC it now shows it as an optional OS on boot!!! When I reboot the machine now it stops and asks which OS to boot Windows 10 or AVAST CLEAR UNINSTALL! Really? I will not harp on why I am having to uninstall avast from 60 clients computers but his will be the final straw for sure for all the rest of our clients.
Sorry to hear the issue with Avast Clear.
If you are using a console, you can do a mass uninstall from there.
In Avast for Business (Cloud Console) simply remove the computer from your group and it will uninstall at the next checkin
For Avast Enterprise Admin, create a Deployment task and choose the type to uninstall managed products