The Father of Lights is the most powerful being. He actually created the Force and all of existence. Nakhash is the second most powerful, for he is able to disrupt the creation process used by the Father of Lights and send the rest of his kind, the Celestials, to flee the dawn universe. The Bedlam Spirits are below the Celestials.
There's also the difference between a Celestial's true form and the physical avatars that they've taken on. So there's that.
Well, that list predates Supernatural Encounters. So outdated.
If true, SW has nothing. The Father of Light's power level should be around multiversal+, nowhere near the megaversal level.