The Negative 4 are literal "negative" clones of the Super 4 team.

They debuted in the episode "Negatives" of season 1, created by a malfunction of  Dr.X's duplicator. The Negative 4 (or Negative team) only want chaos and destruction in the world, at contrary of the Super 4 that want peace and harmony. 

The Negatives were then defeated (and "deleted") in the same episode. 

In the second season, in the Super Bad episode, they came back thanks to a malfunction of the duplicator machine caused this time by the magic of the Crystal Sword (the King was doing again the ceremony that we saw during the episode Convoy of Honour) that hit the machine with his magical wave.

In the end of the episode the Negatives are shown captured by Alien's tribe, but is not clear what is going to happen to them.