Saruman

Saruman is a major antagonist in the Lord Of The Rings series and unlike the obsessive, wretched excuse for a creature known as Gollum was a dark and powerful wizard who conveyed an air of nobility tainted by obvious tyranny.

Originally Saruman was opposed to the evil of Sauron but would later abandon his morality in order to try and gain more power for himself via allying with his former enemy - this theme was quite common in the series, of power corrupting and the inevitable destruction such things bring to a character: Saruman was no exception and despite his considerable power he would ultimately fall victim to his own quest for power.