Dark Valefor
Location : Besaid Island Village Enterance
By far, Dark Valefor is the easiest Dark Aeon of them all. Make sure you have the Auto-Phoenix ability to protect any party members from be downed. When you battle the Dark Aeons, you should have Break HP Limit, this is crucial when battling any of the Dark Aeons. This battle shouldn't be hard. When Dark Valefor attacks with his Overdrive, you should summon a Aeon to take the blow.

Dark Ifrit
Location : West Sanubia Desert
Ifrit proves that the Dark Aeons get stronger as you fight more. Ifrit can easily down one of your party members, which is why you should have Auto-Phoenix. Also, definately you need to have Break HP Limit. Ifrit will counter all attacks dealt to him, the damage will easily be 9,999 damage. Make sure you continue to use Overdrives, and you sure sacrifice Aeons so you can not take the damage.

Dark Ixion
Location : North Thunder Plains
Ixion will not be that hard, Ixion will regularly use Thunderaja, Having Thunder Eater, or have Yuna us NulShock will work. Again, make sure you have Break HP Limit and Auto Phoenix. Ixion's Full Break cannot be negated. Thunder Eater can negate Thunderaja, but cannot negate his special attack, Aerospark. Make sure you take advatage of heavy damage Overdrives and Doublecast Ultima as much as you can.

Dark Shiva
Location : Macalania Temple Enterance
Shiva is very fast and can attack faster than most of your party. Make sure you have Break HP Limit and Auto Phoenix. When Shiva uses Heavenly Strike, it will have a Death effect. Ribbon or anything cannot prevent it. For that, Auto Phoenix should kick in. Shiva's Overdrive will cause alot of damage to your party.

Dark Bahamut
Location : Zanarkand Dome - The Beyond
Bahamut like Shiva is very fast and agile. Bahamut's Impulse special move damages all of your party. Auto-Haste is what you should use during the battle. Again, the conventional for the battle, Auto Phoenix and Break HP Limit. Bahamut will constantly use Overdrives so be prepared and use an Aeon to take the Blow.

Dark Yojimbo
Location : Cavern Of Stolen Fayth
Before the battle, make sure that you have Auto-Haste, Break Damage Limit, Auto Phoenix, and equip Ribbon. Yojimbo will attack quicky so Auto-Phoenix will become important. Yojimbo's overdrives will inflict Status Effects and make sure you keep barraging Dark Yojimbo with strong and fast attacks, as well as effective Overdrives similiar to Wakka's Reels.

Dark Magus Sisters
Location : Mushroom Rock
This battle should be easy. You battle each of them each seperately. Cindy, Mindy and Sandy are extremely easy if you have Break HP Limit, Auto Phoenix and Auto Haste.