The earliest time you can get this is a early as Sequence 2, when you're first introduced to the Smoke Bombs. The game will prompt you to press
to equip them. Ahead of you, there are three guards, one standing on a platform, and two underneath. Hold
, and use
to widen the scope until all three enemies are highlighted. Press
to smoke them. If done correctly, you'll get a count of three towards the achievement. You don't even need to run past the enemies.
From here, simply reload checkpoint, and you'll start where the three enemies are. Rinse and repeat until achievement pops. It takes literally seconds to get three done this way, and the achievement should unlock rather quickly.