Right, so out of the 15 replies to this post, only one had any sort of information the OP wanted to hear...
Try re-posting this in the Lich King or Warcraft franchise forums, maybe we'll see some more sense then.
Oh, and I'm not all that clued up on my Warcraft lore - but I'd say Kil'jaedan is probably stronger than him, although I don't think there's any real hierarchy of power in the Warcraft universe, it tends to switch and change a lot. GB's Lich King article needs filling out!