Unstoppable Force and Immovable Object -- Altina and Ike.
Ike can survive with full defense support and full HP. I checked with my past failed attempts. The WoM healer was the problem and after that, Ike tanked everything and protected everyone. He needed all the attack buffs to defeat Altina in one round because of Vantage.
I haven't tried it yet, but if you have a tank that can survive Altina, Hardy Bearing might be the only way to defeat her. Good luck, summoners!