I’ve always thought it must be tough being an atheist superhero in one of those big superhero universes. Think about it. Many heroes have firsthand knowledge of the presence of gods, angels, the afterlife, and demons. And while many superhero characters are rarely identified as belonging to any particular faith or lack thereof, the only atheist hero I can think of is the Michael Holt version of Mr. Terrific, and he was an atheist because he couldn’t believe God would let his wife die as opposed to the idea of just not believing in God. Holt was also as a member of the Justice Society, where he spent time with the Spectre, the embodiment of the Wrath of God, and probably had some encounters with Zauriel the angel on the Justice League.
But if we really want to see how not accepting something despite it being right in front of his face works, we really need to discuss Dr. Terrance Thirteen.