Ancalagon

Ancalagon (or Ancalagon the Black) was the first winged dragon to be seen in Middle-earth. Near the end of the War of Wrath, Morgoth unleashed Ancalagon from Angband to fight against the Valar. Although he managed to push the Valar back, Ancalagon was eventually slain by Eärendil. From high in the air, the dragon fell on the Thangorodrim mountain range, which were crushed by his descent.

Even after his death, Ancalagon was remembered as being notoriously strong. When attempting to convince Frodo Baggins to take the One Ring to Mount Orodruin and cast it into the volcano, Gandalf commented that not even Ancalagon could have destroyed the ring.