Horde HoardG 30

To unlock this achievement you simply need to destroy 10 zombie hordes in one day / one sitting. While driving you will run across zombie hordes and they will quickly make a break towards you. The game will notify you of the horde and they will also appear on the map with a vision cone. The best way to destroy a hoard is with a vehicle. Use either your door to side swipe them or run them over with the back of your car. Using the front will damage your car and eventually make it inoperable. Destroy 10 of these hordes and the achievement will be yours.