This giant beast is tough a foe to defeat. It has a backhand slap which can kill Zack in one hit. Be sure to have a Raise status before fighting this enemy. Cast Regen and Wall on Zack at the start of the battle, then try to run in a wide, clockwise circle (it has to be clockwise to avoid the Karura's left hand attack) while casting Graviga on the enemy. When its HP is low enough (around 5,000 points), finish it off with sword attacks from behind.
Vajradhara is the ultimate primordial Buddha, or Adi Buddha, according to the Gelug and Kagyu schools of Tibetan Buddhism. Achieving the 'state of Vajradhara' is synonymous with complete realisation.