How to delete user in Linux

To delete user, you can use userdel command. Refer below syntax:
$ userdel [options] <username>

Example:
$ userdel anil

To remove the user's home directory pass the -r option to userdel:
$ userdel -r anil

Default values of userdel command are taken from configuration file /etc/login.defs  for RHEL (Red Hat) based distributions. Debian and Ubuntu Linux based system use /etc/deluser.conf file:

 # /etc/deluser.conf: deluser configuration - Debian / Ubuntu Linux only.

# Remove home directory and mail spool when user is removed

REMOVE_HOME = 0

# Remove all files on the system owned by the user to be removed

REMOVE_ALL_FILES = 0

# Backup files before removing them. This options has only an effect if

# REMOVE_HOME or REMOVE_ALL_FILES is set.

BACKUP = 0

# target directory for the backup file

BACKUP_TO = "."

# delete a group even there are still users in this group

ONLY_IF_EMPTY = 0

# exclude these filesystem types when searching for files of a user to backup

EXCLUDE_FSTYPES = "(proc|sysfs|usbfs|devpts|tmpfs)"