DJ Hero 2

You need to get 12 stars in Dj Shadow setlist in "Ibiza: Encore" with hard difficulty to unlock this achievement. Note that you need to get the 12 stars in one go playing the whole setlist of 3 mixes. I.e. Adding up the stars in high scores does not necessarily count towards this achievement.

Take advantage of the power decks and pick the one you find most useful with your abilities. I used Scratch Master to unlock this achievement and I'd recommend it as the first choice since there is a lot of scratching in the setlist.

This achievement stacks up in this order:
Master Of The Empire (12 stars in medium difficulty)
Grand Master Of The Empire (12 stars in hard difficulty)
Supreme Master Of The Empire (12 stars in expert difficulty)

The easiest way to get this is to make sure you select the right turntable. You unlock the "powered" turntables through normal gameplay, so the trick is to pick the right one. On this particular set, I used the platter tapper one, which gave me more points for each platter button I hit. If you're not so good at the taps, then you can probably do it with the scratch master deck.

Of course, this implies you have some skill. Unfortunately, the special decks can't do everything, but if you're pretty close to getting it, they sure do help.