The New God Orion explained why his father Darkseid can never be truly defeated. DC's God of Evil and most iconic villain, Darkseid is the ruler of Apokolips and a threat to all reality, defeated only at great cost by the Justice League. However, in the dark future of Kingdom Come, it's revealed that Darkseid is dead and gone... and yet his evil remains as strong as ever.
In Mark Waid and Alex Ross’ Kingdom Come, Superman has come out of his self-imposed exile and reassembled the Justice League to help guide the lost and destitute Earth and its overwhelming superhuman population. Having overcome his dislike and fear for the disgraced hero Magog. Superman sees the Justice League’s protection of Earth and battle against evil as an escalating war. He travels to another world to seek counsel from Orion, a former ally and the current ruler of Apokolips, only to find him steadily taking on the appearance of his infamous father.
When Superman points out the similarities, Orion responds “So it was written to be. Our story has always been a generational one.” While he initially explains it as another case of sons becoming their fathers, Orion elaborates that he sought to change Apokolips once he dethroned Darkseid. He was shocked to learn that the people only wanted him as their new absolute ruler, considering freedom to be just as terrifying as fascism. Darkseid is not just a terrible individual but the God of Evil, and when he is slain, that position still needs to be filled.
Darkseid is integral to the structure of the DC Universe. The necessity of his existence was further reinforced in the New 52’s Darkseid War. In the story by Geoff Johns, Jason Fabok, and Francis Manapaul, the Justice League and others witnessed Darkseid’s death during his battle with the Anti-Monitor. Once dead, reality was thrown out of balance, and members of the Justice League were recruited to become the new New Gods in his place, nearly driven mad by their new powers and responsibilities. Lex Luthor became the God of Apokolips, taking on the appearance of Darkseid much like Kingdom Come's Orion. This would end only when Grail, a rogue Amazon and Darkseid’s secret daughter, used Superwoman’s baby from the Crime Syndicate world to help resurrect him. Darkseid may be evil, but his death creates a vacuum as reality tries to find a new host for the forces he embodies.
These instances prove that there will always be a Darkseid if there is evil in the universe and that if you kill him, you will only take his place or watch someone else do so. As the embodiment of evil, the only way to truly beat Darkseid is to create a better world. But as long as there is hate, oppression and brutality in the universe, Darkseid will exist in some form, and even killing him just means someone else is forced to effectively replace him in body and soul.