AVG Support Community
In order to get my system back up:
I could not get the USB or DVD drive to boot. That may be an issue with this machine or it may be something to do with the issue. I tried an external DVD as well, without success.
Then I tried using F8 to go into safe mode but in Win 10 it defaults to ignore that. I went online and found out how to change that to a legacy configuration. That allowed me to get to F8. Safe mode didn't work but I noticed at the bottom of the list there are some new options (at least since I last needed F8) and one of them is Disable Early Launch Anti-Malware Driver. I used that to get the computer back and then was able to get to a running system. Then I was able to remove AVG.
During the troubleshooting, I also went in to the Windows\System32\Drivers and renamed all the avg*.sys to avg*.old. That changed my ability to get to the Advanced items because it kept failing with a missing avgboota.sys file. I'm not sure how this affected my final solution.