How to uninstall ns2 from Ubantu

Uninstall just ns2

sudo apt-get remove ns2

This will remove just the ns2 package itself.

Uninstall ns2 and it's dependencies

sudo apt-get remove --auto-remove ns2

This will remove the ns2 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 ns2 then this will work.

sudo apt-get purge ns2

Or similarly, like this ns2

sudo apt-get purge --auto-remove ns2