He can be a Handfull, He has the Highest Magic Defence possible in the game "255" And has has a HP of 1,300,000 HP He's also immune to any weapon-based attacks and absorbs all kinds of elemental spells. And he justs laughs at Physical attacks no matter how high your strength is..
Cast Hastaga or whichever you have on one of your Characters in the battle, Don't forget that Jumbo is always in Reflect Status, SO If you cast reflect on one of your characters in this battle it will help, then cast Slow on that character in Reflect Status, That way slow will hit Jumbo Flan. you could also try it with Blind or Doublecast Ultima and use Copycat,
If you want to take him down using Anima, Your better off using her PAIN, because its is not weapon-based and is a magical attack. and therefore should do 99,999 damage, depending IF Yuna is pretty Beefed up.
If Jumbo Starts taking Anima's HP down, use Lancet to heal her. it may be wise if your Anima has also learned Haste, Disp, Shell, Regen, Ultima, and maybe even Curaga.. Jumbo will, "as you say" Cast Regen on himself if his HP drops, just Dispel it and Keep Paining him..
