This achievement can actually be won easily along with all of the difficulty achievements in the game. Start up the game and play on easy all the way through. Once you reach the last boss (Sonny), you will want to wear him down as you would any other boss fight.
Just before you deal the last blow, pause the game and change the difficulty to Impossible. You will unlock all of the difficulty achievements at once and didn't need to go through the headache of playing on hard (or impossible)!