Disable MsMpSvc from command line
Solution 1:
The Microsoft Antimalware service is protected in various places against being disabled, because this is an attack vector used by certain types of malware. Unfortunately when we have cause to legitimately disable the service, we are then unable to do so.
Solution 2:
Override the permissions with SubInACL, set the service to manual in the registry, then reboot.
There is no point in killing a service that is designed to not be killed, you disable its boot entry instead.