To get the Line ‘Em Up! Trophy / Achievement you should use a single shot to kill two enemies in the main campaign. This Trophy / Achievement will give you one Bronze trophy or 20 gamerscore points depending upon your console.
When you will be completing the first episode, try to get this Trophy / Achievement while interacting with Berry. He uses the Magnum Python which is famous for taking down multiple enemies in one shot.
Now all you have to do is look for the exact moment when two of the enemies are lined up and use the Magnum Python to get this Trophy / Achievement.
Resident Evil: Revelations 2 is a survival horror game and will support cooperative gameplay on console platforms. The first episode launches with a decent start being the first of the four episodes.
Watch the following video on how to get Resident Evil Revelations 2 Line ‘Em Up! trophy / achievement.