To unlock this, you will need to get 180/180 on the remix tour and you will face the Beastie Boys after the credits. This is going to be one of the toughest achievements in the game. Make sure when you start your remix mode, you have practiced enough with the team you have chosen. Some of the Boss battles are going to be incredibly tough, especially the games of 21. Make sure to get a good start and don't hesitate to restart the match if your opponent catches fire. See this thread for any additional boss strategies.