Bahamutt

Bahamutt is a colossal dragon encountered by Mario and his allies while exploring Bowser's Keep in Super Mario RPG: Legend of the Seven Stars. Both Chester and Magikoopa can summon him to help them in battle, as he is indeed a powerful foe. Bahamutt has a lot of HP and above average stats. Besides regular biting attacks, the dragon can resort to the special moves Iron Maiden, which triggers a Fear status ailment, and Drain.

Despite being very strong, Bahamutt doesn't seem very confident in his own abilities, as revealed by his Psychopath thought.

Trivia

 * Bahamut (with one "t") is a powerful dragon from the Final Fantasy series and Bahamutt's namesake. The two creatures, however, hardly look alike.
 * There is an unused sub-species of Bahamutt who resembles Boshi, with purplish coloration and pointed sunglasses. It can use the move Flame, though it has no psychopath.
 * Bahamutt has quite a few relations to Yoshis. Its Japanese name is similar to Yoshi's name and the creature's body shape resembles Yoshis. If a Yoshi Cookie is used on a Bahamutt, Yoshi will swallow it and produce a Yoshi Candy item (which is normally earned if Yoshi fails to swallow an enemy).