There's way more than three and it depends what you mean by 'greatest'. Do you mean greatest as in the most positive or beneficial or in the sense that their motives were felt regardless? I mean I could say Einstein for being a brilliant scientist and theory producer, Hitler for being the example of what not to be while at the same time helping along the technology of missiles which helped us go to the moon and designing the modern highway systems that are used all over today. He may not have thought of that specifically but none the less under his administration such things took shape. And lastly Bill Gates for breaking in the computer age in a whole new and very profitable way. Those are just three random innovators who shaped our planet, for better or worse.