SO MANY TO CHOOSE FROM.
I am going to say SUPERMAN VS MUHAMMAD ALI for right now.
EDIT: I was going to say Swamp Thing #34 where Abby has sex with Swampy be eating a piece of him but is Alan Moore’s Swamp Thing REALLY a superhero comic???
Also, I really just want to post every issue of Grant Morrison and Frank Quitely’s All Star Superman
Or OR OR! Alan Moore’s Whatever Happened to the Man of Tomorrow!
OR OR MORE ALAN MOORE and Brian Bolland! The Killing Joke.
Goddamn you Will Hines for putting this question in my brain.