Smaug

Smaug is the main antagonist of J.R.R. Tolkien's 1937 book The Hobbit as well as the 1977 Rankin/Bass' animated film of the same name and The Hobbit: The Desolation of Smaug. The opening antagonist of The Hobbit: An Unexpected Journey and a posthumous antagonist in The Hobbit: The Desolation of Smaug as well as Tolkien's book Return of the King.

why was he proposed?

 * He's responsible for driving the draws out of misty mountains.
 * Angerly attacked the city of dale as well as Laketown.
 * Has no mercy to anyone.
 * Cares for nothing but his gold and has no redeeming qualities.

Why was he rejected?

 * His worst crimes are Burning Citys and is little more than a generic dragon.