The dragon that guides you. He is the best character in the entire game. I would kill every last inhabitant in that game before I harmed that dragon. He also has the single greatest line in the game...
"What is better - to be born good, or to overcome your evil nature through great effort?"
If you did indeed kill Paarthurnax, then consider yourself fortunate that I can't invade your game with my character, for you would be hunted down. My character was virtually god like by the end. Every stat maxed. Then there was a way to reset your stats back down and build them up again in order to go above the previous max level... that was done as well.
You should be ashamed!