The list of ways in which the King of Comics, Jack Kirby, changed his medium is endless, but he had one more trick up his sleeve that DC Comics wouldn't let him pull.
After tensions over creator's rights drove him from Marvel Comics in 1970, Kirby crossed the street and started making comics at DC, where he crafted his own personal sci-fi mythology that's come to be known as Jack Kirby's Fourth World. Many of the powerful cosmic characters Kirby created in this saga, including Darkseid and Orion, are still used in DC continuity today, and Darkseid in particular has become one of the most powerful supervillains in all of comics. When Kirby left the Fourth World, it was free for other DC talent to play with, and creators including Grant Morrison, John Byrne and Walt Simonson have added their own pieces to the mythology of those characters. That might never have happened, though, if Kirby'd had his way.
In the early 1980s, DC planned to reprint those early '70s Fourth World stories in a new series of books, and asked Kirby to come in and create an all-new 12th issue that would concluce his epic comic The New Gods, as well as a brand-new graphic novel to follow. Kirby and inker/artist Mike Royer started work on the new New Gods story, which Kirby planned to title "On the Road to Armagetto."
After some early pages of the story's art were already completed, though, DC squashed the issue. Why? Well, because Kirby wanted to use the story to lead into the graphic novel The Hunger Dogs, which Kirby originally planned to conclude with the deaths of, among others, both Orion and Darkseid. It would have been a definitive ending to those characters scripted by their original creator, but DC already had plans to include Darkseid in a toy line and an animated series, so he couldn't possibly be killed off.
Kirby couldn't have the ending he wanted, so he and Royer reused some of the "Road to Armagetto" story as part of what eventually became The Hunger Dogs, and Kirby wrote an all-new story that would serve as The New Gods #12. Darkseid and Orion stayed alive and continued to battle each other long after Kirby was gone, and the rest is history.
Of course, even if DC had agreed to let Kirby kill off the characters, there was nothing stopping them from bringing Darkseid and Orion back. This is superhero comics we're talking about, after all. You have to wonder, though, if Kirby had killed them, would other creators still be using them? Kirby's name carries a lot of weight in the comics world, and the Fourth World was very much his baby, so the characters would no doubt have been treated differently. As it is, the moment that could have altered the future of DC Comics became a lost story.