Rock Band Metal Pack

As the achievement description says, you get this one for playing "Screaming for Vengeance" in a Score Duel. Instrument does not matter, nor does the difficulty level selected, nor does the level of competence while performing during the Score Duel.

Me, I turned on two guitars, started a Score Duel with Guitars on Easy, and left the instruments on the couch while I went to mix myself a drink. Five minutes later, the sofa and I had successfully battled to a scoreless draw, and the achievement was mine. (I did it while making a gin-and-tonic, but it should probably work while procuring snacks or beverages of any sort.)