What I could never get over... Windows Defender (and all other client-side AV) is effectively pointless if you are operating as administrator on the machine. A carefully-crafted powershell command (running in an elevated context) can completely erase all traces of Defender in seconds.
Once you get your hands on a TrustedInstaller session, you are pretty much in god mode.
Once you get your hands on a TrustedInstaller session, you are pretty much in god mode.