20 Below Zero (PvZ2)


 * For other uses, see 20 Below Zero.

Difficulty: Easy-medium

20 Below Zero is an achievement in Plants vs. Zombies 2. It requires the player to freeze 20 zombies with a single Iceberg Lettuce using Plant Food. It is worth 5 points on Game Center for iOS devices and 500 XP on Google Play Games for Android devices.

Strategies
The easiest way to obtain this achievement is to play Ancient Egypt - Day 24, which is after the Sun Boost upgrade. Working in columns from left to right, fill as much of the board as you can with Tall-nuts. Allow the level to play out, but be ready to act quickly. Do not panic when the Explorer Zombies start burning the Tall-nuts. Moments before the Explorer Zombies reach the lawn mowers, a large amount of zombies will come onto the screen via sandstorms. Once they have appeared on the board, very quickly place an Iceberg Lettuce and freeze every zombie via Plant Food.

Another easiest way is to use a Boosted Iceberg Lettuce in levels. This will save Plant Food and it will freeze every zombie when it is planted on the lawn.

Another way to earn this achievement is to wait until the final wave of a three or four flag level and then use the Plant Food on the Iceberg Lettuce once they are all on screen. Check your achievement page to make sure you got it and repeat as necessary.

Another way is to go to the Pyramid of Doom, wait for the screen to fill up with a lot of zombies, then plant an Iceberg Lettuce and use Plant Food.

Trivia

 * This is currently the only achievement in Plants vs. Zombies 2 in which its first word starts with a number.
 * Its manner is very similar to the same one in the original game, only requiring Plant Food to succeed.
 * This makes it the only achievement to return from the original game.