You create an account on a new computer to install applications and updates. Before finishing, you want to delete the user and reset Setup Assistant.

launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServicesLocal.plist
dscl -f /var/db/dslocal/nodes/Default

cd Local/Default/Users
delete updateuser
cd ../Groups
delete admin GroupMembership
delete staff GroupMembership
exit

rm /var/db/.AppleSetupDone
rm -rf /Users/updateuser