Benn Beckman is one of the most overrated character in One Piece.
One piece SBS i believe its Volume 8 or 5 don't remember. oda was asked this question. and look at the answer.
R: Who are the "One Piece" characters with the highest and lowest IQ's?! Okay, that's enough for today.
O: I'll tell you. But when I say "in One Piece". I really mean, "of all the characters introduced in One Piece". And having cleared that up, the character with the highest IQ is Shanks' first mate, Ben Beckman. He is a great crewmate, who possesses astonishing wisdom and strength, and advises Shanks. And right after him would probably be Captain Kuro, then Nami, etc. Now as for the lowest IQ… I can't decide the worst one. They're all idiots.