UNLOCK: Capture at least one of every fiend in Macalania (Macalania Woods and Lake Macalania).
BOSS ANALYSIS: The boss will only use two attacks: Hades Claws and Blade Shower. Hades Claws will damage you and restore some of the Espada’s HP; it will also automatically KO you, or Poison you if you survive via Deathproof/Ribbon. It also used as a counterattack. Blades Shower is just high physical damage to a single character, used after every four Hades Claws (including those from counterattacking).
MAIN STRATEGY: This boss has Auto-Regen, meaning it will regenerate a random amount of HP each turn, up to a tenth of its maximum HP (which is 280,000), so it can regen up to 28,000 HP. To beat that, you pretty much have to get at the boss before he can get at you. Thusly, the fewer turns you spend healing, the better - thus, Auto-Potion with X-Potions and Auto-Phoenix also work very well here to save some turns. And rounding out with Auto-Haste helps you outspeed the boss.
When the fight opens, you’ll want to begin with two things: Slow on the boss, and Full Break or Banishing Blade. This will half its nasty Agility (to 26), Strength (22), Defense (50), and Magic Defense (80). That makes things much more manageable, although you will want to have Deathproof or Ribbon on your armor to not have to worry about Hades Claw’s instant death proc. Once the boss’s stats are depleted, you simply attack and heal from there on out. Try to favor physicals, since the boss takes 1.6x more damage from them than magical attacks.