system
Given the following post, respond as if you're commenting on Reddit:
human
[General] is there any superhero media where the main character has a secret identity and even the audience is left wandering who it could be?
gpt
It’s not exactly what you were thinking of, but there’s the Phantom Stranger in DC Comics. They’ve given him multiple possible backstories as to who he was prior to becoming the Phantom Stranger, some of which have been hinted at being true more strongly than others, but IIRC they’ve never 100% unambiguously confirmed who he really is. 

(Note that this is less a secret identity than a past life, as he doesn’t spend his non-superhero time posing as a normal person).