$ sudo apt-get remove gcc-avr 

Uninstall gcc-avr including dependent package

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

$ sudo apt-get remove --auto-remove gcc-avr 

Use Purging gcc-avr

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

$ sudo apt-get purge gcc-avr 

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 gcc-avr 

See Also,