Exdeath

Exdeath  Hp : 49 001  Weaknesses : None

If you have Big Guard, use it. Gp Toss is by far the best attack to use against Exdeath, just make sure you have enough Gp to spare. Cure using Cure3 or White Wind. He will use Meteo, Flare and Holy occasionally. If he uses White Hole, have someone use a fenix down, then a soft, followed by a strong cure type spell.
 

NeoExdeath

NeoExdeath  Hp : ?????  Weaknesses : None

Gp Toss is good here too, same as Big Guard. Just make sure you can cast Esna after he casts Grand Cross which is a status attack.  He also uses level 3 magics, Holy, Flare, Meteo and Hurricane.  Just stay healed and use Gp Toss non-stop.