Before you haters mention Proteus or Godly or w/e, take a moment's pause and look into history more. Recency bias does not do justice to the truly overrated players. I would like to get this discussion started by offering the first name into the pot:
Zauper.
He talks a lot and retells his glory ages in Serenity with quite a bit of artistic license. I'll clue you in on the truth though: beyond having an awesome sounding name, his kingdom was never really good. For one, the results do not match the hype, even I have more crowns than him. For another, he was thoroughly exposed when he came back with Odyssey in a much weaker era.
Let's not sugarcoat it, for someone who boasts the amount that he does, he's just a big nub.