How I Defeated "Angra Mainyu" in Final Fantasy X-2

Angra Mainyu is one of the most challenging bosses in Square Enix's Final Fantasy X-2. He is 20 times tougher than the final boss (way more HP too; 333,444 to be exact). No matter how high the level of your characters, this fight will take awhile. To be on the safe side, it's recommended that the player has about an hour to spare. It took me about 45 minutes to defeat Angra Mainyu during my first round of gameplay without "New Game Plus Data."

The strategy I used limited my abilities to rely on items only. No magic at all! Here's two reasons why:
1.) Angra Mainyu will constantly unleash an attack that will drain all your MP. If you use magic or attacks that require MP, you'll end up spending every turn trying to gain your MP back only to have it taken away again shortly afterwards.

2.) Tawrich and Zarich are Angra Mainyu's two sidekicks and they love casting Black Magic spells. I needed all the HP I could keep, so I used a Star Curtain to cast "Reflect" so that all of Tawrich and Zarich's spells will bounce off my team and back onto them. Less damage on me, more damage to them. If you do the same, remember that once you cast "Reflect," you cannot cast any White Magic spells on your party, especially "Cure" or "Haste." If you do, it will bounce off the party and cast it on the boss and then you'll just die faster.

With that being said, mage DressSpheres were pretty much out of the question. So instead I used two Dark Knights and an Alchemist. This combination makes a very powerful team with limited magic and good healing. My girls were were set up as follows:

Rikku
Alchemist DressSphere - For the essential "Mix" ability. Knowing the Mega-Potion or Phoenix Down Stash abilities was also convenient.
"Supreme Light" Garment Grid (For Auto-Life).
Ribbon Accessory (protects against all status ailments). If you do not have the ribbon accessory, then it is recommended to equip something that protects against confusion and poison. An HP boost is a good suggestion as well.

Yuna
Dark Knight DressSphere - All status ailment proofs were learned. Confuse Proof was essential!
"Valiant Lustre" Garment Grid (increases physical and magic defense by 20).
I used accessories that had Silence or Darkness protection, as well as an HP boost.

Paine
Dark Knight DressSphere - All status ailment proofs were learned. Confuse Proof was essential!
"Downtrodder" Garment Grid, so she could absorb "Demi" attacks.
I equipped accessories that increased strength and magic defense. HP boost, physical defense, or things that can protect against Silence or Darkness are also good suggestions.

Other Equipment Suggestions
Angra Mainyu will cast high-level Black Magic spells such as "Flare" and "Demi," so you can also equip accessories and grids that will minimize the damage.
Also, if you desire, you can equip the Speed Bracer on a character to generate a constant "Haste" effect. Angra Mainyu will occasionally cast "Dispel," undoing all your hard work. Equipping this accessory can be like an insurance policy just in case that happens; it will allow you to quickly throw your "Protect" and "Shell" barriers back up again.

Items Checklist
I had the following items in my inventory; I suggest other players should have the same:
99 Potions
99 Hi-Potions
Mega-Potion(s)
Phoenix Downs
Mega-Phoenix(s)
Eye Drops (if characters are not Darkness proof)
Antidotes (if characters are not Poison proof, Depends on the abilities learned as a Dark Knight)
Echo Screens (if characters are not Silence proof)
Remedies
Lunar Curtains (Casts "Shell" on the party)
Light Curtains (Casts "Protect" on the party)
Star Curtains (Casts "Reflect" on the party)
Chocobo Feathers (Casts "Haste" on a single character)
Chocobo Wings (Casts "Haste" on the party)
Optional Items:
Soul Spring (Absorbs HP and MP from enemy)
Stamina Tablet (Increases max HP on one character)
Stamina Tonic (Increases max HP on party)

The Fight
Using the Darkness attack with both Dark Knights worked best for me. As you probably already know, the Darkness attack drains your character's HP for each use. So I had my Alchemist mixing Mega-Potions (Potion + Hi-Potion) and healing ON EVERY ROUND! Whether or not the party needed to be healed, I mixed and used them anyway. I also occasionally used Mega-Potions from the Items inventory list and the Alchemist's Stash ability.

I had my Dark Knights use the non-healing items so the Alchemist would be soley focused mixing and curing. Chocobo Feathers and Wings were used to caste "Haste' on the party, especially the Alchemist (so she could Mix and heal faster). I also used Light Curtains and Lunar Curtains for "Protect" and "Shell" barriers, respectively.

Tawrich and Zarich only have about 5440 HP. Knocking these two out was helpful, but Angra Mainyu would always cast "Full Life" to bring them back.

As I was mixing, I could see how many potions I had left in my inventory. By the time I dropped down to about 20-30 potions, Angra Mainyu was defeated (again--333,444 HP).

As I mentioned before, it took me about 45 minutes to defeat Angra Mainyu with this strategy. Afterwards I went back to the Cactuar Nation, spoke to Benz, and earned a few more much deserved completion points! If you do the same and do not receive any points, try completing the "Cactuar Hunting" mission first.

I know it sounds dull doing the same attacks over and over for such a long battle, but it was well worth it, especially if you want to get the full ending. This fight is definately a challenge when it comes to keeping the girls alive!