Ancalagon

The defender and destroyer of Thangorodrim, the mighty "Rushing-jaws" was the greatest monster ever born in Middle-earth. He was the epitome of Fire-drakes and the father of Winged Worms. Hundreds of feet long and possessing a fiery breath capable of destroying an entire forest in a single blast, Ancalagon could drive away an army or slay whole tribes unaided. His spells rivalled those of the Maiar and his visage invoked a terror surpassing that of a Balrog.

Fortunately, Ancalagon was killed by Eärendil during the Great Battle. A lucky and skillful bowshot saved Endor from a creature unrivalled in the annals of history. Ancalagon was so huge that, when he fell, he shattered his the Black Enemy's fortress beyond repair.