I recommend you to create a new admin user, log your old user out, open a terminal as the new user and run
sudo deluser OLD_USERNAME
to delete the account from the system config. After that, all files are still there. Then you can run
sudo find /home/OLD_USERNAME -type f -exec shred -vzfun1 {} \;
to shred all files in your old user's home directory so that they can't be restored (overwriting once with random data, once with zeroes, then removing the file). After that, you can
sudo rm -rf /home/OLD_USERNAME
to remove the empty directory structure. Make sure you have no typos though! —
Byte Commander 1 min ago