"Well, that is a difficult question. I'm not really sure how I'm here. But if this group came here in Shin, who know what all effects it has? From what I've seen, most of the normal Demons are about the same level of strength, though. Satan is probably twice as powerful as any other Demon. At least. And there are other demons far stronger than that one. I saw one that could just disappear from existence and attack you without exposing itself."
OoC: To give you an idea of the strength difference.
http://www.mangarush.com/manga/666-satan/48/p-5
That giant there, is a Demon. And he is literally being forced by Satan to bow to him. To be fair, he's in his first (of three) form. And his final form is the size of a city, but that is pretty damn impressive.