A Quick Tip by Garyuu
How to Beat Chaos (not Feral Chaos)
I believe that some people here are playing Dissidia Duodecim and Dissidia1 OR have imported their data from the Dissidia1 and still attempt to grind with Chaos. I'll tell you what Chaos makes easy to beat (with a snowball's chance in hell of surviving) so you can be able beat him at lvl 100 with low level characters. Just make sure you have accessories and/or bonuses to give you more exp.
Fist things first, use the BRV-centric rule in Battle Setup. It increases the critical damage you deal to enemies, even more so when blocking attacks.
1. Watch out for his first attack. When using low level characters, Chaos will use either Condemn (the vacuuming pillar of fire) or Divine Punishment. Otherwise he'll use Soul of Oblivion, which can easily be countered at the start of a round.
2. (Important Rule!) Stay Above Chaos. In a moment when Chaos is not attacking you, you must jump to a higher altitude. Press Up+R button repeatedly to dodge and go higher. Altitude is what makes Chaos fairly predictable, because eventually he'll simply dash towards you. This is when you block his dash and counterattack. However, there's a chance he'll use other moves as he air dashes towards you, so be careful.
3. It's easier to use bravery attacks that knock Chaos down, such as Tifa's Falcon Dive. Altitude still makes Chaos predictable, so block his air dashes and stay above him. Characters like Laguna don't have attacks that knock down enemies, making them difficult to beat Chaos at lvl 100.
Dodging his moves.
1. Condemn can be easily dodged when you see it coming. If you don't, game over.
2. Divine Punishment. It's not as hard to dodge as people think. All you need to do is stand still. The fire pillars won't hit you except the swords surrounding you. You have to wait for the right moment to dodge them and counter Chaos. This is difficult to pull off in the air. You can still stand still, but once you land on the ground, the frame delay can cause you to be unable to dodge when you need it at the last second.
3. Scarlet Rain. Try to block all of the fireballs he conjures before he launch this HP attack at you. If one fireball hits you, game over.
4. Flame cyclone (his BRV spin attack). It's simple, just block repeatedly. It's magic damage, so you do not get so much as a critical bonus.
The most difficult thing to counter is his Dive Kick. In the first Dissidia, blocking his dive kick rebounds, but now it is unblockable, which is lolderp. If he doesn't air dash towards your block using the altitude rule, he'll most likely use a dive kick and transition to a Condemn attack.
That's as much as I can cover now. Hope this is more useful.