Nas and Jay Z had some beef back in the early 2000s.  Heated words were exchanged though songs, radio interviews, TV, all of it.  It was very publicized and  the verbal warfare got pretty heated.  So much so that Nas planned on lynching an animatronic Jay Z at the 2002 Hot 97 Summer Jam in New York.  Hot 97 pulled the plug on that idea and Nas pulled the plug on performing, but not before he had some robotics engineers put together a Jay Z robot.  Check out the robot and the videos to some dis-tracks Nas and Jay put out for the language.