According to Oda, Beckman has the highest IQ of all the characters introduced in the East Blue saga. Across his voyages he’s learned a lot of experience, with an incredibly advanced intellect and great thinking capabilities.
When the Red Hair Pirates arrived at Marineford to stop the war, Beckman was able to climb on to a Marine ship’s mast and sit on it, all the while pointing his flintlock at Kizaru, without the latter noticing.
Admiral Kizaru chose not to fight him, even though he had just fought the First Commander of Whitebeard’s crew and Whitebeard himself.
“One Piece: Vivre Card Databook” confirmed that Benn Beckman is almost as strong as Shanks!
His card says that Benn is incredible powerful in terms of physical combat. The card even says that “Comparable to Red Hair’s, this man’s existence is feared by even the powerful warriors of the New World!!”