There is no easy way to go about this. This guy is arguably the hardest boss in KH history, and if you wanna complete those reports you've gotta do it with each character (yes, that includes Terra).
This fight is easier with Ventus and Aqua (though still very hard), granting that you go in with a specific strategy; that is, Spam Dodge Roll/Cartwheel and Surge attacks and be at a fairly high level (45+ at the very least on Standard).
Practically every one of his attacks kills you in one or two hits, regardless of level on STANDARD, so Second Chance, Once More and Leaf Bracer at the least are a necessity. Interestingly enough though this is the only fight in the game where you want to have LESS abilities equipped, because the more you have equipped the more he will spam some of his cheaper attacks. Also having Defender and the Haste abilities, as well as Thunder or Fire Boost maxed out is helpful. HP boosts are essentially useless, as he generally knocks you down to 1 HP in one hit, so there are two states of being in this fight HP wise: some or one (or dead), and it just makes him prone to spamming his cheaper attacks. (Meteor does little damage but can take off a little bit, leaving you vulnerable for a killing blow on 1 HP, so don't risk being on low HP for long).
Now onto his moveset:
Basic Combo. This is easy to dodge away from, and you will generally see the attack pattern the more he does it, so as soon as he finishes up go in for an attack. If you get hit by this make sure you're hovering over Curaga in the options once he finishes the combo to heal up
X Flame. Not quite sure what this is called by but he slowly jumps up in the air to shoot the namesake at you. This is a great moment to attack him as it is slow to wind up and easy to dodge, not to mention it being a singular attack
Collision Magnet. This has actually been nerfed since the PSP release. In that version if he grabbed you it was almost a death sentence, this time you can easily dodge out of it (but you are left vulnerable in the air for a short time so hit the ground dodging). Again, another good opportunity to attack him as in this version it is pretty easy to avoid and punish him for it.
Aeroga. This attack is unlike anything else in the game. If he connects with this your Command Deck will be scattered, forcing you to collect it again on the battlefield, which can be terrifying if he's got you down to 1 HP with it. This can be interrupted, though.
Lazur Beems. This attack involves him doing an ominous slow walk with lasers going everywhere at you, which can catch you by surprise if you aren't careful. Has killed me before.
Sonic Impact. This is a rare one but he will occasionally flit around the arena like this so be careful
Raging Storm. A much faster version of Aqua's attack here. Don't even bother attacking him when he's doing this.
Clone Rape. Now this attack is pure bullshit at times, and what can be affected the more abilities you have equipped (i.e. he will spam it more often.). He will summon a volley of clones of himself to relentlessly pound you for at least 20 seconds, so it is prudent to keep dodging during this (although he can and usually will catch you with one of them). You can either wait it out or go in for a Surge when they're all grouped together to dissipate them. If he catches you in it, then there is a VERY strong chance that you will be stunned after the clones dissipate (which I honestly don't remember happening on the PSP version), leaving you wide open for a final blow from him which he will 99% of the time take.
Meteor. THIS can catch you off guard. Generally easy to avoid but might get you at some points. Summons about 2 or 3 Meteors in a blinding flash of light. with a large shockwave.
Web of Death. Only way I can describe this one and it can be potentially catastrophic. With this attack he will grab you and a countdown will start in which you need to spam X to get out of. Be warned that the countdown will gradually go down faster each time he connects with it until it actually becomes impossible to break out of and winds up being an instant kill (I think). Mercifully he doesn't seem to use this often but results may vary.
Paralysis. I dunno exactly how to describe this one but similar to the Web of Death he just grabs you on occasion. I think you just spam Dodge or the Left Stick with this, I dunno.
At 50% health he will periodically (read: frequently) turn invisible, and combine this with his other attacks (mercifully excluding his Clone Rape). You can attack him during this phase, but it is incredibly risky, so I would advise against it.
You will want to be attacking him at the end of these moves generally, and then immediately dodging out of the way once you have a moment to. DO NOT attack him normally (this is essentially suicide); use Surge attacks in the fleeting moments you have to attack him. Most of your time will be abusing Aqua and Ventus's i-frames in their dodges, and even then it isn't 100% reliable as he can still get you with an attack out of nowhere. Terra is a whole different beast. Rumour has it the DEVS weren't able to beat him with Terra, so what hope do you have? Ok you do, but he's a LOT harder because his Dodge is terrible and has very few i-frames in it and cannot be spammed. Make sure he is VERY high levelled; moreso than the other two, and to have all of the relevant abilities equipped.
This fight is as much luck as it is skill, even with Aqua and Ventus. Sometimes you will get unlucky and he will get you with an attack that kills you, so just persist and you will bat it eventually. Anyone who says they beat him on their first try is a dirty rotten liar.
Good Luck!