Orion did kill Darkseid in Countdown, but nobody liked Countdown. Also, Darkseid's death allowed him to begin his plan to destroy the universe, all because Orion was too bull-headed to consider the consequences. It was only thanks to Superman and the Miracle Machine that the universe survived. Yes, Orion fulfilled his divine destiny but he almost ruined everything for everyone. So, thanks for nothing, Orion. Hope the adrenaline rush was worth it.