Recommended level: 25

Recommended Keyblade: Treasure Trove

Recommended Shotlock: Dark Volley

Zack is a very quick and powerful enemy, which makes him quite challenging to face as Terra. He is the boss of Olympus Colosseum and has two forms.

First round
This round should not be challenging at all, feel free to charge Zack and launch a full scale offensive assault, his attacks are easy to read and you should block, jump, and dodge accordingly.

Second round
This is where things get hard, he gets much quicker when consumed by darkness and his combos are enough to kill you if you don’t have enough HP or Second Chance and Once More. The gambler can begin the battle by immediately charging up your shotlock, if this works you’ll deal a good amount of damage to him and he won’t touch you. The trick here is to be defensive, watch and wait, you do not want to get caught in his combos. It is recommended to have two Curagas in your deck at this point for when you get low on HP. You can constantly dodge him and attack him with a magic barrage or you can watch him carefully and get him in a corner and attack him relentlessly. 

Either way the most important thing is to not get attacked when the dark aura surges around him. Be quick to dodge and be patient and you should win the fight without too much trouble.

Recommended level: 60-65
Recommended Keyblade: Metal Chocobo, Oblivion, or Ultima Weapon, something that rebounds well
Recommended strategy: All out offensive
Run time: 35 minutes

Phase 1: Ansem and his Guardian
 The first phase of this boss battle will be a simple duel between Sora’s party and Ansem and his Guardian on the beach of the Destiny Islands. Nothing too difficult, just hack and slash at him and avoid or counter his one or two physical attacks. Whenever his Guardian comes in front of him either find a way around to attack from behind or you just wait for him to return behind Ansem. Use have Aeroga cast on at all times because at that level it is not only a defensive spell, but when attacking from close range it also does continuous damage to the enemy. This phase should be quick and easy.

Intermission:
 This is the only break you will get until the end of the game, use this to heal, stock up on items, switch Keyblades or whatever you need to do. Have your items stock set to nothing but Elixir’s at this point, use the AP bonus you got from the last phase of the battle to update your abilities if you can, just make sure you are in prime form.

Phase 2: Darkside
 You will head inside somewhat of a dome where you will face another Darkside heartless, just like you did in the beginning of the game. The same strategy remains, go for the hands and jump whenever it punches the ground. This should be a quick fight, you won’t even need to cast Aeroga.

Phase 3: Solo fight with Ansem
 Just like last time you won’t be fighting with Donald and Goofy. This will be just lie the last time you fought Ansem except he’s a bit more formidable this time. As soon as the battle begins cast Aeroga and begin attacking, however, when he sends his Guardian to come possess you, the attack command will occasionally change to possess, so if you are willing to risk the damage that comes from being frozen for a few seconds keep attacking, or else you just dodge roll out of the way until the Guardian leaves your body. The only other attack that you should worry about is when he sends his guardian shooting out of the ground to attack. When that happens just dodge roll in a circle non-stop until the attack ends.

Phase 4: World of Chaos
Now Ansem has become a giant ship and you have lost your friends once again. What you need to do is float to the top of the ship where the giant Ansem is and attack him mercilessly and heal as needed. Of course you’ll need to have Aeroga cast since you’ll be having to be right against him to fight, so the additional damage helps.After you defeat him he’ll go into hibernation inside the ship and you’ll have to launch your assault on the ship itself.

Shadow room
 You’ll now find yourself in a pitch black room with the only light being a blue glowing Heartless symbol in the ground with a ton of shadow heartless inside. Use this room to restore your MP by attacking the Shadows and restore your HP by the HP orbs they drop. You shouldn’t have to heal in this room. After the Shadows are gone, a sort of heart will appear in the center of the room, attack it and keep doing so even after the HP runs out to continue to restore your MP.

Attack the Pods
Now you’re outside of the ship again and these pods will be shooting lasers at you. Plain and simple, take them all out. After this a Portal to Dakness will open where they were, head inside immediately.

Darkball room
 Again you will find yourself in a pitch black room, but this time it is full of Darkballs. They tend to do more damage so you might have to heal a few times, but the upside to this is that they drop MP orbs and you reunite with Goofy in this room. After the Darkballs are gone the heart of the room will reveal itself so just attack that and keep slashing to keep restoring MP.

The Ship’s Head
 Head down to the bottom of the ship now and attack the grotesque head of the ship, cast Aeroga and just mercilessly attack with Goofy. You will have lasers being shot at you but keep attacking, healing, and casting Aeroga until you’ve defeated the head. After it’s defeated the mouth will open revealing another Portal to Darkness and you must promptly head inside.

Invisible Room
 Now you’re reunited with Donald as well as Goofy to fight off a room full of Invisible Heartless. Donald should heal and protect the party but if you ever get in the red take matters into your own hands. After the Invisible’s are gone the final heart of the room will appear. If you’d like you can take this time to heal and use an elixir, a good idea. Then kill the heart.

Inner Ship
 A previously inaccessible area of the ship will now lift it’s barrier and open itself up to you, fly inside, ignoring everything else, and head for the big lavender boil looking like thing that appears to have a drawn on face and attack it. Killing it will stop all other attacks and end this mini phase of the battle.

Ansem (again)
 Head back up to the top of the ship where Ansem has emerged fully healed and do the exact same thing you did in the first phase of the ship battle. Launch a full on offensive and he should be dead within a minute or two. After that pat yourself on the back because you’ve just beaten Kingdom Hearts.

I was asked by one of my followers t give them a walkthrough for this boss so I decided to do so, and start a series about them.

Basic Requirements:

• First off, before you even think about facing him or any optional boss, you MUST have all your abilities leveled up. Have all your hastes filled up, leaf bracer, second chance and once more, and everything in that vein. 
• Recommended Level: 45 - 50
• Recommended Keyblade: Ultima Weapon or Pixie Petal 

Aqua
 The strategy here is magic. Notice he only has on bar of health, but his defense is insane so physical attacks don’t do much. What you want to do is arrange your command deck to be full of nothing but Seeker Mine, and Hi-Potion, I say Hi-Potion because curing takes too long, and even though you’d be protected, you’d get hit during the recovery time.

In battle all you do is dodge, and lure him into your Seeker Mine. That is all. Be patient and learn his attack pattern so you don’t get hit.

Ventus
 With the the right strategy this will be the easiest battle in the game, it will take literally twenty seconds. Ready to hear it?

As SOON as the battle begins, use Tornado on Vanitas Remnant twice, then hit him once with your Keyblade. Congratulations, you’ve cheated the system.

Terra
 Good luck, I have nothing to say about him because he cannot dodge.