Probably the hardest achievement in the game. You must beat the entire story on Hard without ever changing the difficulty. Before starting Build a Label, make sure you go to options from the main menu, and change the difficulty via game options.
DJ Scratching is the key to making it through this mode in one piece, so always use it! Figure out ways to keep your opponent still enough to grab, and always get them into the hazards. They deal more damage than any of your attacks, and will bring someone down fairly quickly if you focus on it. While either of the of the starting styles will work, it's recommended that you start with Street Kwon Do, as you grab faster than other styles.