Who does Darkseid fear?
Most would consider Darkseid to be a Superman villain first and foremost, but in the comics, Martian Manhunter best qualifies as Darkseid's rival.
During the massive fight, Orion ultimately kills him by ripping his heart out, which created a firepit of Apokolips from Darkseid's chest cavity (in reference to the prophecy of their final battle).
Darkseid (pronounced Dark-side) is a new god of the Fourth World, one of the most powerful beings in the DC Multiverse. As the tyrannical ruler of Apokolips, he frequently comes into conflict with Superman.
In the known DC Multiverse, one name stands above all others when it comes to supreme villainy—Darkseid. Ruling over the hellish world of Apokolips, Darkseid doesn't merely mean to conquer a planet or subjugate his enemies—he seeks to rob the entire universe of its free will and replace it with his own.
Darkseid is not afraid of Superman. He didn't come to Earth himself because Steppenwolf owed him thousands of worlds as a repentance of the Great Betrayal. Steppenwolf was afraid of Superman and referred to him as 'The Kryptonian'.