I forget if Duodecim has it, but the original game, after beating Chaos the first time (in a scenario you may be ridiculously overleveled depending on how you approached Shade Impulse), Selphie actually would tell you exactly how to deal with ALL of Chaos' Moves. don't think the properties of his moves changed, especially since fighting Chaos practically doesn't exist outside of 013 Storyline anymore and Quick Battles, but here's what I remember...
Brave:
Claw Swipes: Block. Pretty straightfoward.
Wave of DOOM!: Dodge. Blocking it staggers you, though the move isn't really painful, just annoying.
Spin Attack:Block Repeatedly. The move seems to guard break cause it hits so many times and is a projectile (Thus doesn't stagger him), but actually isn't it, you just need to continually follow up. It is Melee too so you can't dash through it either. Note that a lot of defensive HP Attacks are great against this move; WoL's Shield of Light is a prime example as it blocks the entire thing *AND* is insured HP damage on him.
Dive Kick: Dodge or Block. I think Blocking staggers you, but he doesn't follow it up, and you can recover out of it fast enough; if you're in air, it tends to put him at a disadvantageous scenario for anyone with good camping (Hi Bartz!)
Teleporting Shoryuken: Just dodge 3 times. Its basically like fighting a Hell Vanguard.
HP Moves:
Divine Punishment: stand still (or just fall if in air) until the...6th? flame, then dodge the swords that converge in the middle. If you can dodge them, you likely have avoided the attack. It takes time figuring this move out. Note there are some moves that completely MOCK this attack. Terra's Tornado is the most famous example, as it blocks the entire first part AND punishes him before he fires the last part, as he does not have invincibility frames during it.
Flamethrower of Doom (forget its name): Attack him before he fires it; he's vulnerable to EVERYTHING while charging it, and its charge time is ridiculous.
Demon Dance: Dodge multiple times. About the only thing you can do is learn the timing; basically, dodge whenever he teleports, ideally to the side.
Scarlet Rain: Block the Meteor Part, dodge the HP Damaging Fireball. Like Divine Punishment, some HP moves can actually trivialize this attack, and block the entire thing, though some require better timing than others (Terra's Tornado works for example)
Utter Chaos: Dodge the sword slashes as best as possible, though don't fess if yo screw up. What matters is not being on any of the circles at the end, so RUN OFF THEM. Its pretty easy to dodge for most characters not Ex-death.
Chaos' fight is really more intimidating than it is hard but most of his moves have some way around them and the key is figuring it out. After that, its more a case of "don't screw up" though there are some bullshit things like Divine Punishment being completely arbitrary if its going to hit you with the flame pillars or not (I still can't quite figure out how it determines that. It'll only happen if you're moving, though, but how much seems completely arbitrary)
Frankly, I find Feral Chaos a much stupider fight if you ask me.
