Ghostrunner

I actually got this achievement without trying and had it surprisingly pop when I didn't think it would. I forget to mention in the video, but you wanna be on the mission Echoes and play until you come across the first sniper. There is a spot to the right of him that you can jump up on, and then jump up and hit him with the Tempest ability and for some reason this apparently counts as killing him without getting near him. After reading the other solution mention an ability I didn't have yet I thought I'd have to come back and do this, but nope. The other method with Surge doesn't look too hard, but this may be slightly easier and you can get it on your first playthrough without having to return on a replay.

Start the Level "Echoes" and Play until you reach the Checkpoint were the first Sniper enemy appears.
Then use the Surge Ability and use the Upgrades Size, Speed and Range to make things easier.
Simply walk a bit closer from the Checkpoint and hide behind one of the Pillars and aim with the Surge Ability to kill the Sniper from far away.

Good Luck on Obtaining it Guys