Look at history. Bahamut is tameable... as are all aeons, and can be defeated. I think the Allagans used him as the power source for Dalmud... probably in a crystal. He is only super powerful when you are relatively weak.Looking at FFX: "Bahamut possesses the auto-ability Break Damage Barrier. This enables its attacks to exceed 9999 HP damage right from the start. Bahamut has high strength, Defense and Magic attributes. Bahamut's regular attack causes more damage than any other aeon's. Bahamut can also cast the highest elemental black magic spells." As awesome as Bahamut sounds.... remember when you summonned him he rarely could take out a major boss without a lot of help.