[thatguy]

Level up at the islands closest to heaven or hell. Get lionheart. Get lot's of aura for Squall. Equip it all to squall. Use aura with lionheart (limit break not sword.) She will die within 4 Lionheart limit break attacks. Also get hero for her Apocolypse attack. Also be prepared with elixers and megalixers.
Strategy: Use aura on Squall and keep pressing triangle until his limit break appears (do not worry about anyone else in your party they will just hold you down, do not cure them, do not waste time, have them cure Squall)
Strategy B: Get Selphies' limit break and keep going through it until you find "The End," use it and congradulations you've beaten the game (very difficult to come across in Selphies' limit break.)