Star Trek: D·A·C

Easier way to get this is on a Conquest game using the Flagship, simply look around for the power up (it is a yellow shield) and then head over to the enemy capture point. once you are inside they will flood you, activate the shield as soon as there is three or more. Start firing upon them and you should get it straight after the 3rd enemy is destroyed. If you only destory 2 enemies and happen to catch an escape pod then you will still get the achievement. It is easier to focus on the enemies though as the escape pods shoot off so fast.

Also make sure you have the cheat activated.
LT, Y, X, X, Y, RT

Play a Conquest match with max AI, input the Kobayashi Maru code and select the fighter. Fly around collecting yellow orbs until you get a powerup that looks like a shield. Fly into a point that is being defended by 3 or more enemies, activate the powerup and hold down right trigger while aiming to easily destroy them.