Call of Duty: Ghosts - Piece of Cake Achievement/Trophy Guide
Piece of cake
Storm the common room and kill everyone without taking damage on Veteran.
Piece of cake achievement/trophy can be obtain during Mission 11 : Atlas Falls (Veteran Difficulty). This is trophy/achievement is one of the most difficulty to get.
During the mission, you will get to a double door that you need to breach, and then your ally will push you away from the explosion.
Make sure that you keep all your grenades and flash bangs for this section, and it is best to use any weapon with a red dot sight.
Cook a flash bang and throw it into the middle of the room. When it goes off run and take cover behind the counter directly in front of you. You can keep firing while running for cover.
While behind the counter, throw another flashbang into the middle of the room. Crouch to see the location of the enemies and then toss a grenade into each corner of the room and that should take out most of the enemies.
Wait for your allies to kill few more enemies and then slowing poke your head out and kill the remaining enemies. When the final enemy is killed and your ally says "All Clear!" you will earn the achievement/ trophy
Note : that if you "push up" but stay behind cover so that your allies will move up and kill enemies. In case you get hit (indicated by a red blink on your screen), press pause and restart the checkpoint.