Here’s a regedit to disable:
Reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender" /v DisableAntiSpyware /t REG_DWORD /d 1 /f
and here’s an msiexec remover, quiet; not sure if this still works:
msiexec /uninstall windowsdefender.msi /quiet /log uninstall.log