The secret here is that you don't have to actually pass a level to get this achievement.
Use level select (turn it on in the settings menu) to start on any non-challenge level past 10 (I used 12, but it shouldn't matter). When enemies start appearing on the screen, just shoot once into a dense area. If you hit an enemy, just sit still and die until your game is over. You'll finish with an accuracy of 1/1, or 100%, and the achievement will unlock.
If you miss that first shot, then just reset the game and start the level over again.