Remove a user from a group

 net localgroup <group name> <user> /delete
e.g. C:\> net localgroup Administrators savillj /delete

How to add user to a group

net localgroup administrators anormalUser /add

Change or reset domain user password with command

net user [username [password|*] /domain
Example: net user iSunshare Abc12345 /domain

Delete/remove domain user with net user command

net user [username] /delete /domain
Example: net user iSunshare /delete /domain