So how do you do it? Instead of gaining Achievements by working your way through levels, this game awards five different Achievements based on increasing your combo counter. At a hit count of 10 and 20, you gain 150 points each, at 30 and 40 you earn 200 points a piece and once you up the counter to 50, you get the last 300 points.
In most of the game, this is actually a challenge. Most parts have you taking on three or four enemies and by the time you get to the next wave, your time is up and the combo counter is reset. There is one place in the game that will send just the right number of people at you at just the right rate. Unfortunately for The Burning Earth, its right at the beginning.