I believe the mission that nets you this achievement is actually called "Mob of the Dead". After meeting the talking skull, you end up in a cemetery with a spade. The goal here is to keep the undead at bay with your shovel. Make good use of the various power ups and if you get mobbed, use the escape points on the right and left areas of the screen.
It might take a few goes to get it, but provided you try and keep moving and not get corned, you should be fine. Make sure you hit the zombies with knight helmets with a low attack as they are immune to high hits. Once the counter hits zero, run to the center and pick up the ticket to end the mission.