The evil genius only exists in fiction.
An evil genius cannot exist in reality, because in reality, intelligence and evil are incompatible. A genius acts rationally, and history constantly proves that it is rational to be good.
Genius and evil are two terms that are nearly impossible to define, but most people know it when they see it. Adolf Hitler was evil. Osama Bin Laden was probably evil. Albert Einstein was a genius. Bill Gates is probably one too.
It’s not that evil doesn’t pay; genius and evil both pay, in some sense. Bill and Osama both have mansions, and could probably afford the most expensive bacon at the grocery store (though I guess Osama would pass). The difference is that Bill is living a comfortable life that leaves a trail of advancements and improved lives. Osama is at the bottom of the ocean riddled with bullets, and has left a trail of destruction and ruined lives.
Osama and Adolf did gain power, but was it through genius? I doubt it. They excelled in some areas—charisma, mostly, and probably a good helping of being in the right place at the right time—but I doubt they were geniuses. Not in the sense meant here: extreme mental ability for coming to correct conclusions.
On both an individual and a societal level, it is rational to be good. More often than not, the correct choice between a good option and an evil option is the good option, all things considered. Murdering a person you can’t stand may be easier than altering your own life to get away from him (say, packing up and moving away), but on an individual level, murder will probably put you in jail or dead yourself, and on a societal level, allowing people to murder willy-nilly wouldn’t be conducive to happiness and productivity.
That’s why the evil genius doesn’t exist. Even if the impulse to do evil was there, a true genius would take a moment, and think “hmm, considering all the consequences, maybe genocide isn’t such a spiffy idea.” If The Joker was really so smart, he’d figure out a way to resolve his Batman problem without blowing up innocent people and getting thrown in Arkham again and again.
Evil cannot result from the cool calculated machinations of a genius. In real life, evil is in the hot passion of an argument when a knife is nearby. It’s in the subtle biases of a politician whose values are misguided. And in that sense, evil is in all of us; luckily we also have an inner genius to play superhero.