Fun achievement to get! Blow up the world!
To obtain, simply play as Corn and press
. Often! In the direction of a zombie!
The simplest way to get this really quickly is to play a solo round of Garden Ops. Try planting plants sparingly around you so you can get zombies grouped up around fighting them and you can shoot in the shucks and get a bunch at once! Or just play through using it at whim. You'll surely get it in a game or two.
My only tip is to make sure you aim where the target is going to be in about 1 or 2 seconds. The shucks take a couple seconds to charge up and they fly relatively slowly. Direct hits do way more damage than the splash damage.