okay I'll give you a suggestion
and you might not like it
and you will
fuck it up
one time Marvel event:
continuity wide 616 storyline about all the heroes, aliens, cosmic powers, gods, infintes .
gear up, prepare, do their bucket lists before leaving.
becoming one with the universe.
disappearing into thin air
ceasing to exist.
you gotta give them a story about creating a blank slate before you can give them one.
just look at Warhammer Endtimes.