In terms of all around high level functioning Batman or Doom probably takes the cake.
In terms of raw intellectual might Reed and Metron surpasse anyone I can think of. Some characters have probably have knowledge beyond even them in specific areas though.
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Graffiti outside Latin class.
Sed quis custodiet ipsos custodes?
A juvenal prank.
From both Marvel and DC , this is the concrete list of who is smartest.
1. Reed Richards and Doom. It is close to call
2)Lex Luthor
3)Ray Palmer
4) Mr. Terrific & Tony Stark tied
5)Bruce Wayne.
I put Bruce Wayne behind Luthor, Palmer, and Terrific because DC itself has stated that Mr. Terrific is the 3rd smartest man in the DC universe. Reed and Doom have battled for years and have been shown to be the top 2 brains in the Marvel universe.
Doom. it takes monumental amounts of talent to compensate for his ego and arrogance... and yet somehow, with all his preening, haughty and abrasive ways, he still manages to keep it all together, to pose a threat to the universe and to even have Thanos' respect!
of all creatures in the Marvel Universe, I'd put Galactus top, then Thanos then Warlock or something...
Didnt he also found a way to get to heaven/meet "god" not too long ago, before Civil War? Also, He's bound to solve Earths issues as poverty, hunger and what not(per recent issue). Reed is a good candidate for smartest man.
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"A lie, Mr. Mulder, is most convincingly hidden between two truths." Deep Throat.
The real Peter was captured by the Skrulls just after the events of the other!
They'd developed technology capable of deceiving Mephisto so they could use him to destroy the Earth heroes time line and many any since of their history completely chaotic!
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None of them sparkle!
Sig by Scythe!
Hey no one mentioned The Beast or Forge. Lobo is also supposed to be a super genius believe or not. The smartest guy all around is most likely the Exemplar Stonecutter.