Anima can use Oblivion and Pain against you, two attacks you used against fiends in Final Fantasy X. She can also inflict various status effects, so protect yourself against them by equipping Ribbons. Anima is weak against Holy, so you can have a Warrior use Excalibur or Yuna as a Trainer use Kogoro Holy to deal heavy damage. Have your other girls heal and use other strong attacks, like a Dark Knight's Darkness ability. Be ready for a long fight, because taking down this aeon's 36,000 HP can take a while.