The Smartest in the World

Who, in pure intellectual prowess and inventive ability, is the smartest character on Earth among these three?

Who is smart enough that, in a hypothetical world without invincible being born, would be able to defend the earth against the Viltrumite invasion lead by Omni-Man through sheer scientific know how alone?

For fairness reasons, I would like to remove Robot's experiences in the Flaxan dimension.