To uninstall unity-greeter-badges just follow these instructions.
/ubuntu/vivid/universe///install/index.html Additional badges for Unity Greeter Ubuntu 15.04 universe/misc 0.4-0ubuntu1
sudo apt-get remove unity-greeter-badges
Which will remove just the unity-greeter-badges package itself.
sudo apt-get remove --auto-remove unity-greeter-badges
This will remove the unity-greeter-badges package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for unity-greeter-badges then this will work.
sudo apt-get purge unity-greeter-badges
Or similarly, like this unity-greeter-badges
sudo apt-get purge --auto-remove unity-greeter-badges
|Description||Additional badges for Unity Greeter|