TYPE ON TERMINAL to make a list of all users of your system
cut -d: -f1 /etc/passwd

REMOVE NOW AVAHI USER
sudo deluser avahi

LIKE THIS SCREENSHOT i grab someone that make an login entry on my system
I HAD TO KILL 813 !!
sudo kill 813
then i did again sudo deluser avahi
and sayonara!!


TRY THIS COMMAND TO SEE WHAT PROCESSES IS WORKING WITH WHICH USERS
ps aux