I always like villains that are suave and have the trappings of being civilized. While I like the Joker (who doesn't) I perfer the Bond villains stroking their pure white cats with some witty line at the ready. My Six Evil Gentlemen are a good example. In my world when the Victorian era rediscovered spiritualism, six neer do will men of means discovered a way of becoming near gods. Since then they have spent time on their estates quietly gathering power.
All the Gentlemen have this in common: They do not age. Nor do they suffer from disease. They even heal much faster than any human. In that respect they are like vampires with none of the limitations. No doubt some of their foes were confused on that point and paid the price when they went after them stake in hand.
By now they hate each other, but they still keep ties. After all they are the only ones who can understand each other, and who else could they brag to? If they were to have a leader it would either be the Corrupting Gentleman or the Gentleman of Love and the rivalry between the two can cause great damage to everyone else around them.
The Corrupting Gentleman is very persuasive. A natural politician. He also knows all your desires. It is this power coupled with his money and political ties that gives him such power. He has a huge web of influence across the world.
The Gentleman of Love can cause any one person to love him madly and completely. He has used this over the centuries to get married again and again and gather lovers. He himself does not love, but he uses these to gather a personal fortune second to none. Unfortunately, his power does not work on the other gentlemen or he'd rule them for sure.
The Unseen Gentleman is a sneak and a blackmailer. He can become invisible at will and is particularly hated by the other Gentlemen. He is, though, very useful all the same.
The Geomancer can see all the sacred and mystic geometries when designing buildings. As such any buildings using his plans are very SPECIAL places indeed with rooms that cannot exist and traps for the unwary. No one leaves his mansion that he does not wish to leave. He has sold his skills to many secret cabals and even governments. He is a retiring soul, however, and does take part of the bickering of the other Gentlemen.
The Fire Lord, as he styles himself, has the ability to grow and shape fire to his wishes. A very flashy power he is often used by the other Gentlemen as muscle. He likes that. He is often found in war zones practicing his skills.
The Wastrel is the least liked of the Gentlemen. He is a hoarder and his great mansion is filled with room filled to the ceilings with garbage. His power gives him the ability to control anything discarded. If you don't think that is a powerful ability consider the sewer lines beneath your feet and sheer volume within. He is also used as muscle when the Fire Lord can't be reached.