You receive this after completing level 2-2 "Will There Be Blood?"
I was using the Invincibility Mode, and my results were.
Total Score: 75,026
Total Time: 5:14.864
Rating: B
You should be able to use Invincibility Mode AND the Clear Area assist option and get a better score all around and achieve this with no problem at all. In the same breath you should unlock the achievement below too
The Meep Meep achievement in Bloodroots worth 103 pointsFinish any level in Act 2 in under 3.5 minutes