Controller is a rogue member of an inter-dimensional society that believes chaos is the key to perfection.
This renegade Controller believes that the ultimate perfection comes from chaos, rather than order, and releases the last Sun-Eater to spread this chaos. Superman was sent to stop him on his own while the Legion stops the Sun-Eater. The Controller's plan was foiled, but at the cost of the Legion member Ferro Lad's life. As he makes his escape, Superman warns him to never appear again.