Darkseid is the tyrannical ruler of Apokolips and a major enemy of the Justice League. Superman specifically.
Darkseid is the lord of Apokolips, an intergalatic despot and god whos single ambition is the absolute dominion over all living things. In this endeavour he has searched the universe for the anti life equation, a formula that will allow him to achieve that goal. He has subjugated entire planets in this quest, conquered infinite peoples and inflicted evil so terrible they are beyond description. His campaign has brought him into conflict with the Justice League and Superman who have stood in his way many times. But Darkseid is not so easily bested, he is intelligent as he is powerful and strong, it will take more to defeat one such as him. Darkseid is evil personified.