Everyone eventually thinks they want to run a badass evil PC, or maybe all the players decide they want to run an all-evil party. This is a recipe for disaster for all but the best groups. Why? Because the whole foundation of D&D is predicated on the party trusting one another and working together. The party has to stay together, or there’s no game. The game is about the party. And if people are betraying each other left and right, the players themselves will realize there’s no logical reason for the party to stay together, and the game will just end with the dissolution of the party.