~Comet Drop on three coughing enemies~

Explaination:

This works best against large groups of drug dealers. They are marked with a blue syringe symbol on the mini-map. They spawn randomly, so you might need to run around for a bit. It doesn't matter what karma you have. Even if you have maxed out your bad karma, the drug dealers will still spawn. They also do keep spawning after beating the story and after clearing out all D.U.P. of each district. Simply throw a Sulfur Bomb at them (Smoke Power). The Sulfur Bomb is unlocked in the very beginning of the game and can be used by pressing L1. Once the bomb hits the dealers, wait for a second and Comet Drop on them. To perform a quick Comet Drop simply stand next to the enemies, jump in the air and then press Square. The more drug dealers there are, the better your chance of hitting 3 at once. Again, it's random how many dealers there are and where they are located. A little jump from the street level will suffice. If you have good Karma you can also buy the upgrades "Corrosive Fumes" and "Giant Sulfur Bomb". It's not needed, but it will increase the duration and radius of the Sulfur Bomb and makes this trophy a tiny bit easier.