Xemnas (Final)

Xemnas is the final boss of Kingdom Hearts II. He is fought a total of three times prior to the fight in various other forms, Xemnas has now taken on the power of Kingdom Hearts and wields light and dark energies to battle Sora and Riku one final time. The battle is fought in several stages as Xemnas loses HP.

Kingdom Hearts II
At the start of the battle, Xemnas will grab Sora and throw him into the air. After this, tendrils of dark and light energy will snake through the air as Xemnas teleports around the player, striking them with his Ethereal Blades. The player must either use the Reaction Command Reversal, or the Limit technique Eternal Session to avoid taking damage. Eventually Xemnas will stop the attack and the three will descend to the ground to continue the battle. Although it is possible to damage Xemnas during this phase, it is very difficult, unless one is using Eternal Session. Sometimes, while dodging these tendrils of energy, Xemnas will deal two kicks to disarm Sora then knock him away. Riku will catch his Keyblade and throw it back to him, just as Xemnas attacks both of them, forcing the player to use the Block Reaction Command to avoid taking damage and continue to the next tier of the battle.

After this, Xemnas has a variety of attacks. He can create a shield to protect himself, summon a clone of himself to distract the player, and launch tendrils of dark and light energy (which also require Reversal to dodge). He can also teleport at will, which in tandem with his clones can make Xemnas difficult to track. Xemnas also spins towards the player with his Ethereal Blades extended, or surrounded by dark and light energy tendrils. These attacks can all be avoided with moderate difficulty, if the player can keep track of Xemnas to know when he is attacking.

Once Xemnas has lost a little less than half his HP, he changes his strategy. Xemnas will begin flying around the area leaving Ethereal Blades in his wake, which fire towards Sora after a moment. These blades can also be avoided with Reflect or Guard. Xemnas will call out "Fire!" just before the blade fire, so the player can anticipate them. Xemnas will also still conjure clones, and he and the clone will launch a barrage of Ethereal Blades at Sora.

Once Xemnas takes even more damage, he will trap Sora in an energy sphere and say "Can you spare...a heart?", apparently intending to remove Sora's heart. At this time Riku will be knocked away as Xemnas continues to drain Sora's HP. Taking command of Riku, the player must fight his way to Sora, avoiding a respawning Xemnas clone who will put up a barrier to knock them back. Riku can pierce the barrier using Dark Aura, which the player should use to keep moving forward - if Xemnas drains all of Sora's HP before Riku reaches him, the battle is lost. The player can also use Riku's Keyblade to attack the clone, but it is much more difficult than using Dark Aura. Once Riku reaches Sora, the Reaction Command Rescue will free him, and the player resumes control of Sora.

After this, Xemnas is vulnerable for a short time, then will use the same technique as he did when the battle began, flinging Sora into the air -the player should likewise use Reversal or Eternal Session to avoid damage. Afterwards Xemnas resumes using the attacks he used prior to his laser attacks - namely, tendrils of dark and light energy and spinning with his Ethereal Blades extended.

Once Xemnas' HP is below half of his final HP bar, he will turn the area dark and summon hundreds of Ethereal Blades to surround Sora and Riku. The player must rapidly tap X (or Circle in Final Mix) and Triangle to activate the Reflect command for both Sora and Riku, otherwise the barrage will surely deplete their HP. The barrage lasts a long time, so this can be difficult. Afterwards, there will be a scene where Xemnas will corner a weakened Riku and Sora, only for Riku to pass Sora his Keyblade. Sora will use the two Keyblades to deflect Xemnas' attack and fling him into the air, after which he and Riku combine their powers and fatally pierce Xemnas with a bolt of energy. Finally, the scene will end with Xemnas hanging in the air with 1 HP left - he will no longer attack, so the player merely needs to initiate a final combo and hit him with a finisher to win the battle.

It is important to note there is no way to avoid Xemnas' final assault. Although the player can deplete Xemnas' HP to 1, at this time he will stop taking damage, even from finishers. No matter how low his HP drops, Xemnas cannot be defeated until after his laser barrage, the player must survive it to deal the final blow. Also, no matter what Xemnas' HP was before his barrage, afterwards when he is hanging in the air, his HP will have become 1.

In the Data rematch, Xemnas instead begins the battle by unleashing his energy spheres to the pair's location, often in front of him, which makes it difficult to land a hit on him. Also, the pauses before he and his clone fire their lasers in succession disappear, and he fires another stream after his ring of lasers attack. Unlike the normal battle, however, it is now possible to avoid Xemnas capturing Sora, primarily by casting Curaga, which the player will most likely do at that point, and he will discontinue attempting the same attack.

Trivia

 * Can you spare a heart can be dodged by using Quick Run repeatedly or blocking with Reflega. But this will only stall, Xemnas will continually use the move until you get caught. In Final Mix, during the Data Battle with Xemnas, the same techniques can be used to avoid this move, using Limit Form, or one of Limit Form's techniques, will also prevent this move, difference being, he won't continually use this move till you're captured.
 * If Riku dies in this battle, it's game over, meaning it's just like if Sora dies.
 * Xemnas' Final Form vaguely resembles Sora's Final Form Drive in appearance.

Video
Xemnas (Final)