userdel  –  Delete a user account and related files 

userdel [-rlogin 

The userdel command modifies the system account files, deleting all entries that refer to login. The named user must exist. The options which apply to the userdel command are:

Files in the user’s home directory will be removed along with the home directory itself and the user’s mail spool. Files located in other file systems will have to be searched for and deleted manually.
Forces deletion while user logged in