This achievement can be earned on several of the arcade levels as well as the "Dish Challenge
." I personally earned it on "The Killing Yard
" with practice and by keeping a combo going throughout the level, but there are much easier ways. Others have earned it on "Robot Rampage
" by spamming the
button back and forth from one side of the screen to the other (I earned over 200 million by doing this on Xbox Live co-op). Then there's always any of the later levels with a level 2 (or higher) chainsaw. With the chainsaw equipped, holding
results in a devastating attack that will land an average of 30 hits on each enemy you hit with it. Chaining this move back and forth between enemies is by far the best way to consistently rack up a high scores. Good levels to try this on include are "Enter the Catacombs
" and "Skyscraper!
", although I'm sure there are several others after those.
Past that, there are always the Arcade leaderboards. Look for any levels where scores over the 100 million mark are relatively common.