This achievement has a very simple, reliable way of accomplishing it. The first thing you'll need is the second skill in the basic project skill tree, which extends your possible overdrive multiplier to X10.
Afterwards, go to any mutie nest. Once in, shoot a couple of there egg... nest things to get a lot of them to spawn. Run around in circles for a few seconds to bunch them all together, and mow them down. You could probably use any weapon in the game to accomplish this, but the slam ability (especially with vortex skill) is easily the most satisfying. Also it helps you quite a bit on your way to this other achievement.
That said, if you want to use the rocket launcher instead, the same idea applies to this achievement.
Skip to 13:31 for Overly Driven