$ sudo apt-get remove libidn11 

Uninstall libidn11 including dependent package

If you would like to remove libidn11 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove libidn11 

Use Purging libidn11

If you use with purge options to libidn11 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge libidn11 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove libidn11 

See Also,