To unlock this achievement, Robin must use his Snap Flash (LT+ B) gadget on the following objects/enemies DURING ONE PLAYTHROUGH:
Unarmed thug
Armed thug
Environmental Object
Titan
The Snap Flash must be directly placed on each enemy (LT+B)-- using quick Snap Flash is not enough (credit to XI AlphaMale IX for discovering this).
A convenient environmental object appears as Robin is infiltrating the enemy hideout (this occurs while controlling Robin the second time; thanks to vSully for the information). There will be a series of cargo hooks on a track that runs behind a sniper. Simply follow the in-game prompts to take out the sniper with your Snap Flash.
The same hook will appear later in the DLC during the Predator area while playing as Robin.
Please note that the only thugs that qualify as Armed Thugs are the ones holding firearms.