Acnologia

The Black Dragon is a powerful dragon the appears to be flying around the contenient or the world. Unlike the other dragons that have withdrawn from human affairs, the Black Dragon has not. While the other dragons appear somewhat friendly to humans, the Black Dragon is most certainly an enemy to all humans.

When Gildarts Clive took on the "100 year quest", Gildarts ran into the Black Dragon on the third year on Zonia mountian. In an instant, the Black Dragon took Gildarts's left arm, leg and an organ leaving him to die before flying away.

Trivia

 * The Black Dragon is the only known dragon who doesn't have a known corresponding Dragon Slayer.