In your opinion, which hero has the most charisma in the campaign?

They are needed... There is nothing like the Overlord in Ashan, or beneath it. Your favorite, Agrael/Raelag, is just a pawn. As are all the other heroes. Everyone trembled before the Overlord. Cyrus and Alaron were afraid to help Alex, their own skins were more important. Agrael immediately fled as soon as he learned that a reward was offered for his head. Tieru was killed by the Overlord's servant.
Only the Overlord figured out how to use two inconspicuous women to turn Ashan into ruins. Oh, what would have happened if Kha-Beleth had escaped from his prison. Everyone feared exactly that.