Instructions
Use Auron's Power Break skill or cast Yuna's Esuna spell as soon as the fight begins. This removes Wendigo's berserk status, dropping his attacks to half their normal power.
Cast Haste on the entire party to speed up their attacks. Cast Protect to decrease the damage the party receives from attacks.
Cast Wakka's Dark Attack on Wendigo. This move damages the monster and has a 50-percent chance of blinding him. If Wendigo is blinded, the effect lasts for three turns. He cannot attack you in this state.
Take down the two guardians next to Wendigo as quickly as possible. This is vital, since they will heal Wendigo with a Potion any time he takes damage. When you knock out the guardians, they cast Shell and Protect on Wendigo.
Cast Dispel to remove Shell and Protect from Wendigo. If you don't have Dispel, summon the aeon, Ixion. Cast Ixion's Aerospark move to remove Wendigo's protection.
Use normal physical attacks or fire spells to damage Wendigo until his HP drops below 10,000. At this time, Wendigo starts countering physical attacks with the "Dukes Up" move.
Attack Wendigo with Flare or Fira when he uses Dukes Up. If Ixion is still alive, keep using Aerospark. Take this time to heal the party with Potions or the Cure spell. Heal Ixion by casting Thunder on him. When Wendigo drops his arms, continue using physical attacks until his HP runs out and he is defeated.