Kill 2 vehicles at once with the Target Locator in the 3rd mission. 25 points.
At the start of 'Get the Hell Off My Lawn' on ONI: Sword Base (load Rally Point Alpha on the mission select screen), grab the Target Locator the onscreen Ordnance marker is pointing to and head through the gate. Head to the rock over on the left and two Wraiths will soon appear in the distance.
With the Target Locator equipped, click the Right Stick to zoom in, set the reticule between the two Wraiths and hold RT to set the marker. With any luck, the two Wraiths will converge inside the red circle and both get pummelled by missiles.
Earning this achievement requires a bit of luck, as sometimes the Wraiths won't act the way you want them to. If you fail to destroy both Wraiths, pause the game and select 'Revert to Last Save' to try again. This video is from our unofficial game guide. You can view the full guide here