I've been trying for a few days now to beat Kaos with only a level 1 Chop-Chop with no heroic challenges, attack upgrades, or hats. I can occasionally dodge enemy attacks long enough to get to the skylander battle with Hex, Gil-Grunt and Flameslinger, but promptly get destroyed as I can't dodge three long range baddies at the same time long enough for them to go away.
So I decided to compromise and have some other character beat of the first round of Kaos, and have level 1 Chop-Chop just battle the second half of the battle. It's really tough because it only takes a few hits to be low on health, and that's when I start to get distracted by the pressure of having a low health bar, and start making more and more mistakes.
This was by FAR my best attempt, and also the most impressive from a gameplay standpoint. I have a few other runs recorded where I get Kaos pretty low on health, but not while dodging THIS wide of a variety of attacks. Often Kaos just shoots the sharks a lot and it isn't as impressive when I just dodge those, but here I was at my "A-Game", yet it still wasn't QUITE good enough. I like to call this video "Chop-Chop vs Kaos: A Valiant Effort".
Anyhoo, sorry if this feels like a plug, but I genuinely wanted to show this to you guys. If I ever record a run where I actually beat him, I'll post an updated video. As for now, you can enjoy watching me fail so incredibly close to the end of a really incredible fight.

Enjoy! And if anyone else wants to try this challenge, make sure to post your attempts too. I'd love to see someone beat it. : )