The most evil person....

[Phervasaion]

And, before you point out that he wasn't a character in LotR, it was his evil which corrupted Sauron, "created" Orcs, Dragons and the like, and tainted Arda with evil. There is no evil in Middle-earth but that it derives its source in him.

Yes you have a point there saucepan man. Sauron was only a luitanant to Morgoth. If i had to chooce who was most evil between Morgoth and Sauron i would definately choose Morgoth.