Evil Genius is more a term used to state a
position in society and to have an impressive effect on the subservients in an
organization than to truly classify a person in and of himself. A notable truth about this particular sect of humanity is that an evil genius, by definition, has a success ratio which approximates the expression '
nil' very
closely.
To put it honestly, most evil genii aren't so fearfully endowed in the mental sense after all. They merely have a few good plans, or an area of specialty. Sometimes, they have none of these, and manage merely to stay behind the scenes, but remain evil genii all the same. The worst case is when a member of this caste is so laboriously hidden from the audience, that the only known thing about this 'evil genius' is that he talks in very strange English, and that he most definitely has hands. Then you don't have a genius nearly as much as you have an owner, because other people are doing all the work.
The evil genii that aren't particularly intelligent are the most fun to work with, because we all know that they started calling themselves evil genii in order to get the respect that they so desperately wanted. They often fail to accomplish even this though, and their take over the world schemes often stem from the inadequacy they feel at having been slighted or ignored as a small child. In some occasions, they don't even want to rule the earth as much as commit vicious acts of vandalism on a cosmic scale, such as blowing up the moon, or the sun, or the moon and the sun, and Saturn (why can't any evil genius want to ice-skate on Saturn, evilly).
Anyway, these genii are usually only clever. But they would never admit it. The only real reason is that 'Clever' just doesn't set people back like 'Genius'. Notice that 'Clever Bad Guy' isn't nearly as intimidating as 'Evil Genius'. Diction is very important. This is your first lesson on the road to becoming an evil genius.