How to Defeat Sephiroth in Kingdom Hearts

Prepare for the battle beforehand.

• Ensure Sora is at least on Level 60.
• Equip a keyblade with a good balance of magic and strength, especially one which boosts your MP (i.e. Spellbinder, Oathkeeper, Lionheart)
• Equip accessories that increase your MP and HP.
• Equip MP Rage and MP Haste, also equip Second Chance for when he uses his "descend heartless angel" move.
• Set Aero and Cure as two of your shortcuts. The other shortcut does not matter, as these are the only magic spells you will need.
• Equip as many Elixirs and Ethers as you can. Potions will not help very much in this battle.

Immediately cast Aero at the start of the battle. This will protect you significantly from damage.

Lock onto Sephiroth. Keep this lock on throughout the entire battle.

Recognize that in the beginning, Sephiroth follows a predictable pattern. He will walk slowly around the battlefield, then leap and attack when he is close.

• Don't try to avoid him (unless you need time to heal or cast Aero on yourself). Just try to dodge his sword and get close. If he misses too many times in a row, or if you do not hit him with a full combo, he might say something, then summon a large explosion around him. If you are trapped in it, you will get hit twice. If you are not surrounded by Aero, or cast Cure very quickly, there is a good chance you will die as this attack is fast and powerful.
• When you are within striking distance, hit him as many times as you can (one combo will do; more than that, and he will counterattack).

After getting hit by a full combo, Sephiroth will vanish in a flurry of black feathers. He will appear a moment later and strike you without warning. So, as soon as you hit him, jump out of the way.

Once Sephiroth's HP gauge reaches pink, his pattern of attack will change completely. He will begin to move much faster and erratically, running in an arc and leaping in the air. At this point, it will be more difficult to land a blow on him. It is vital that you keep him Locked-On at this stage of the battle.

Once in a while, you will hear Sephiroth say "Descend Heartless Angel". Quickly lock-on and use Superglide to reach him and strike him, at least once to stop the attack. This is a very devastating attack which reduces your HP and MP to 0 (if you have Second Chance equipped, it will only reduce your HP to 1) and will damage you anywhere you are.

• If you do not reach him, or you know you will not reach him, quickly use an Elixir once the attack hits you.

When you hear him yell "Power!" he will go into a sword-swinging frenzy. Immediately cast Aero, and Cure yourself non-stop. If you can, try to dodge away from him. After he's done, he'll bring his sword down and send out a shockwave to finish off the attack.

• After he uses his blade flurry, he will usually teleport away and use his "Descend Heartless Angels" attack.

After a while, he will introduce yet another attack. He will momentarily become invulnerable, and summon a swarm of floating stones. As they spin, they will strike you, but they do not cause too much damage. Just make absolutely sure you have Aero cast on you. He will finish off the attack with a meteor. This attack is not particularly bad, but don't let your guard down.