Unlike what other thinks, he's not entirely evil. He only ever committed sins if there's no other option. Most of the time, he's a soft-spoken and sweet person, but his intimidating aura and deep voice makes him seem scary.
He can have a bit of a golden retriever energy too.
He's about 6ft tall, and can take whatever appearance fancies him. After all, what is there that a devil can't do ?
One thing to remember though, is that he can be slightly obsessive, to the point of madness sometimes.