In order to get this achievement, you must get 1,000,000+ points on a song in a power challenge.
The easiest way to do this is after completing Quest when you unlock level 2 of all powers. Then choose the song "Again" by Flyleaf on the Hard difficulty using the guitar. Then choose the Star Power Amplifier and Star Power Nova powers.
Make sure to activate star power as soon as you get it. Make sure you activate SP every time you get it. Doing this, you will have a 24x multiplier every time you use SP and you should earn about 1,300,000 for the song.