For this achievement you must use your worshipers to kill others. It is easiest to do this with your worshipers vs an enemies. The earliest place for this is during the tutorial when it teaches you to how to get followers. If your going this route, don't stomp on the enemies as the tutorial tells you. Just let your worshipers do it as the enemy will never stop spawning if you don't kill their spawn point. Here is a video to help you: (Credit goes to SilentRich Achievement Guides for the video)