Superman Annual: Year One Thousand #1

Synopsis

SUPERMAN AT THE END OF TIME! At the end of DC K.O., Superman became King Omega with the powers of a god. But after pushing Darkseid back to the Absolute World, Superman rejected the Heart of Apokolips... and went missing. Now the story of where he went can be told! The future was infected by Darkseid and his Legion — leaving a trail of death and disaster in their wake — including the Legion of Super-Heroes. Now Superman is using Time Trapper's powers to heal the future and correct the damage that has been done. But Superman's godlike powers are fading fast, and he may become lost at the end of time!