How to remove third-party Kernel Extensions in MacOS Catalina?

Hi, at one point I installed Disk Drill and AVG AntiVirus. I uninstalled both of them using the official, vendor-provided uninstallers, but there are still third-party Kernel Extensions sitting in /Library/StagedExtensions/Applications and /Library/StagedExtensions/Library/Application Support. I have tried sudo rm -rf, sudo rm -Prfd, sudo rmdir, and sudo chmod o=rwx in Terminal and drag to Trash in Finder. They all returned "Operation not permitted" (drag to Trash in Finder just did nothing, no output, KEXT still there). I have also tried to remove them from the Software section of EtreCheck. It claimed to work, but the KEXT's are still there. The KEXT's names are "SecureDisk.kext" (the Disk Drill KEXT), AVGFileShield.kext (one AVG AntiVirus KEXT), and AVGPacketForwarder.kext (another AVG AntiVirus KEXT).

I also don't know how to use kextunload because whenever I use it:

sudo kextunload /Library/StagedExtensions/Applications/AVGAntivirus.app/Contents/Backend/drivers/AVGFileShield.kext

I get "(kernel) Kext com.avg.FileShield not found for unload request.

Failed to unload com.avg.FileShield - (libkern/kext) not found."

I have also full-blown reinstalled MacOS from Recovery Mode but the KEXTs are still there-MacOS remembered all of my files, which is good and bad.

How do I remove these third-party KEXT's if MacOS had protected them like this?