As you progress through the story, you will unlock rope arrows. The achievement may seem hard, but it really isn’t :) . You just need to find enemies standing near roof edges or hiding behind cover that can be destroyed with rope arrows. You can recognize this kind of cover by the rope tied in the middle, which you can latch onto and pull.
Shoot a rope arrow at the enemy. Sometimes they will only stumble or fall over, but if it doesn’t work, just shoot another rope arrow at them.
If you don’t get the achievement right away, don’t worry. You can still unlock it later. Just find some enemies, start running away from them, and hide behind this type of cover so they stay close to an edge. Enemies can also spawn when you teleport to different locations in the game, so sooner or later the achievement will pop.