Conversely, the least attained achievements are "Lamb 2 Slaughter," which asks players to "as an Infected, incap a Survivor who has entered and left a safe room," and "Zombie Genocidest," which requires players kill 53,595 infected. A rounded-down figure currently places both of the aforementioned achievements at 0%.

While the "What are you Trying to Prove" achievement, which requires players to beat all four campaigns on the Expert difficulty isn't at 0%, only 0.2% of the game's population has attained this objective. On a related note, only 2.1% of players have managed to beat a single campaign on expert to accomplish the "Zombicidal Maniac" achievement.