I'll play Devil's advocate (literally)
So what are they like? Pretty unmistakable, actually, and not the sort you can easily ignore or forget. First, they've always got great ambitions, and they won't settle for anything less. Every politician or ruler or rock star or corporate CEO who ever reached the top--whether for good or ill--was a Devil of sorts. Even the best men and women, with grand ideas for improving their countries, have to have the Devil's own confidence in their right to be in command, as well as a love of control, of having lots of people doing what they say, to go after that throne. And while they won't always cheat to gain that throne, they are willing to bend or, yes, break rules if they can get away with it. The ends justifys the means.
Devil people are also seductive and attractive. They have an uncanny understanding of what people really want and know exactly what to say, how to say it, in order to get them to surrender to those desires. "No, no," you say, "I couldn't take that last slice of chocolate cake..." But the Devil knows you want it, and he/she will urge you or just cajole you into indulging.
There is nothing a Devil enjoys more than manipulating people into indulging. Which is not always a bad thing, is it?
That's what Devil's are like. And I've no doubt that you've met at least one already.