An even easier solution than the fight with the 2 titans in the botanical gardens is after you shut down the water pumps after you finish Croc's lair.
After shutting down all 3 pumps, you'll be trapped in the center room with 3 elevators, and electric fields blocking access to the 3 hallways. The trick is to keep dodging the charges of the titan while you take out the other goons. Once you're down to just the titan, stand directly in front of a force field, wait for him to charge, and dodge at the last second. The titan will hit the force field and get himself stunned, allowing you to go to town. Do this twice per segment of his health (he has 3 segments) and at the end, you'll unlock the achievement!