Lex Luthor, the arch-nemesis of the Man of Steel has tried to find out the secret identity of Superman several times and was successful quite a few times.
For instance, in Superman #2, Lex built a machine that allowed him to find out Superman's secret. But later, he denied it as he couldn't believe someone as powerful as Superman would be comfortable pretending to be as weak and feeble as Clark Kent.
Another instance I can remember is from the DC Rebirth where Lois Lane disclosed Superman's secret identity to the public.
However, has Superman ever revealed his identity to his nemesis willingly?
Open to all forms of answers: main continuity, Rebirth, New-52 as well as Elseworld arcs. Trying to avoid the occurrences from the movies etc., looking for answers specifically from the comics.