This can be accomplished by loading the final checkpoint in Chapter 6 on easy very quickly. (That's right....NO need to complete the entire chapter.)
Just use your plasma pistol (No melee or grenades), and only kill required enemies until the objectives appear (press B on the control station, and again to grab the power source.) Use full charge pistol blasts on the two big orks, and keep rolling out of their reach until they drop.
This will end the mission very quickly, and provide you with the achievement.
Enjoy!!!