uninstall bind9
To uninstall bind9 just follow these instructions.
Uninstall just bind9
sudo apt-get remove bind9
This will remove just the bind9 package itself.
Uninstall bind9 and it's dependencies
sudo apt-get remove --auto-remove bind9
This will remove the bind9 package and any other dependant packages which are no longer needed.
Purging your config/data too
If you also want to delete your local/config files for bind9 then this will work.
sudo apt-get purge bind9
Or similarly, like this bind9
sudo apt-get purge --auto-remove bind9