The first battle against Xemnas, is a face to face between him and Sora. During this fight, he will move fast by teleporting and will attack our hero with very long combos and with his electric shield. When it begins to drain the life of Sora, you will have to use the reaction command on the skyscraper to go after him and cancel this effect. The battle is not complicated, it is only a prelude to what awaits you; after defeating him Xemnas will collect the power of KH and disappear behind a door, waiting for you for the final battle, you can save and complete the game if you want before facing him, once done you can cross the door and prepare for the final encounter.
This impressive battle is divided into 4 basic parts:
The first part is to reach him who is sheltering in a fortress similar to a giant dragon, when you arrive before him you will see him sitting on a throne with the form of incorporeal armor on. He has a great sword lance in addition to the organization's weapons (except for Roxas's Keyblade).
This battle is not very complicated, since it will only attack with the organization's weapons such as Xaldin's spears and Axel's Chakrams and it also makes things easier for Demyx clones to be there to do more damage, it also uses its shield from time to time once in a while, one way to tell when you will be wearing it is when it is covered with the cape.
After winning this first battle it will seem to have finished everything, but it is not like that. Xemnas will appear with another dragon that you must destroy part by part mounted on a Jet piloted by Riku and supported by Sora; dodge, block the attacks and fire rays relentlessly to eliminate it after this the 3rd phase will begin.
You will find yourself again before the armor form of Xemnas, now his attacks are faster and more powerful, and he can throw you out of the dragon, in which you will have to use the buildings to be able to return, this time he uses his shield more frequently, and does not use clones a lot, it also attacks with electricity and wind. (It is very likely that it will also throw your companions off the dragon, do not worry as they will return quickly). Another of the attacks that you will dislike the most are those rays of light that he will use constantly around his throne, once he is liquidated you will go to the final phase.
Xemnas will appear as human again but in his final form in a white suit with black parts.
He has 12 bars of life, and will begin the fight by grabbing Sora and throwing him into the air to hit him with thorns and lightning (something he can do for the rest of the fight out of sheer malice). Use the reaction command to dodge it and land to face it directly.
Among its attacks are combos with huge blades of energy, thorns and balls of electricity, it travels fast and creates clones making it difficult to touch and can be very annoying.
Once a few bars of life have been subtracted, it will begin to move faster and attack you with energy beams launched like bullets, it is good to reserve your magic to use reflex with them or to block them directly. It will also catch Sora and drain life from him, during this section you will control Riku and you will have to free your friend. Avoid the Xemnas clone by keeping him away with dark cannon or physical attacks and upon arrival use the reaction command to set Sora free again. When you have subtracted all his life Xemnas will execute his limit attack.
His final move is a field of black limbo that will launch several laser beams at our heroes (use the reaction command and make sure to press both X and triangle so that neither of them is hurt) after this you will see an impressive fight scene that will leave Xemnas with a VT point and it will only be enough with one magic (less reflection and magnet) or one more final blow with your keyblade which will put an end to the meeting, and will give way to the end and the credits.