This Achievement you can earn at the end of the first level(Brad Bossfight).
After Smiley falls into the Garbage container there is a little conversation, then Star starting to talk like *fragghhhlagnlb*
something like this...
Then press X to hit him, but not 1 time you have to do it 15 times, so dont stop hit him until you get the achievement.
Remember : 15 Times maximum you can hit him 40 Times.
--------------UPDATE--------------
In the last mission what is 60% the same as the first level, at the end again press X to hit him.
Video by Armageddon Gaming (MrFraggs)