Balor. Irish Folklore
If you go back far enough, everything turns to folklore. The Irish are no exception, and some of their folklore is spectacular and epic.
Balor was the tyrant leader of a race of giants known as Fomorians. He was said to have oppressed the Irish people from his fortress on Tory Island.
When a child, as the story goes, he looked into a mystical potion being brewed by his father's druids, and this resulted in the development of a large putrid/poisonous eye. With this eye, he could destroy anything upon which he gazed.
"He had a single eye in his forehead, a venomous fiery eye. There were always seven coverings over this eye. One by one Balar removed the coverings. With the first covering the bracken began to wither, with the second the grass became copper-coloured, with the third the woods and timber began to heat, with the fourth smoke came from the trees, with the fifth everything grew red, with the sixth it sparked. With the seventh, they were all set on fire, and the whole countryside was ablaze!"
Needless to say, this could be a considerable issue if you wanted to, say, stop him from oppressing you by just snicking his oversized head from his gargantuan body.
There is a prophecy that Balor would be killed by his grandson... so he locks his daughter in a tower. She somehow manages to arrange a booty-call, and falls pregnant. When the child (Lugh) is born, he is saved by the sea-god Manannán, who raises him elsewhere.
Well, you know how this works. We've all heard a good prophecy. When Lugh comes of age, he nips back to Ireland and leads some pre-Christian Gaelic deities (the Tuatha Dé Danann) to battle against the Fomorians, and kills Balor with a magic spear.
There are many interpretations (and frankly, versions) of the tale of Balor. Many consider it to be harvest folklore, about the battle between blight and plenty... but it doesn't really matter.
Balor is a proper villain, in the traditional sense. All we need now is for Peter Jackson to turn it into a trilogy.