Monsters vs Aliens

You can get this guide in the second part of Chapter 1. After you've finished the first segment in the game, involving Ginormica, you'll get to control The Missing Link. Near the end of his segment, you'll be put on a raised, circular platform, where spherical enemies keep spawning. Your task will be to perform two leap attacks, to continue the story in the chapter. This is an unavoidable achievement and the tutorial on the screen will help you.
However, if you have tutorials off, you need to hold the X button until The Missing Link performs a slow-down ground shockwave-looking attack. Whilst you charge the Leap Attack by holding X, run around so you don't get hit, as you do not need to stand still. When he performs the slow-down ground shockwave-looking attack, use the L Stick to aim at all of the enemies on the screen, then when you've selected them all, he'll do the Leap Attack. Do this twice to get the achievement, and to progress with the story.

In order to initiate The Missing Links leap attack you need to hold down the "X" button until you see that his hands are glowing and a chime will sound, once they're glowing/hear the chime you can release the "X" button, The Missing Link will now pound on the floor and everything will be in slow motion, the resulting shockwave from him pounding on the floor will result in any enemies nearby being thrown into the air, when this happens some small target markers will be around each floating enemy, use the "LS" to mark the enemies and then The Missing Link will attack all the highlighted enemies with a one-hit-kill attack.