I was level 60 something and I beat him in KH2, and my master form was pretty bad.
When you find him, make sure your level 70+, he can kill.
I don't really think anyone will care if Avatar copied KH or not, we all know KH is better, right?
Hello fellow KH fans as you can probaly tell by my name i'm also a Sonic fan (i'm more of a Sonic fan than KH fan.) I hope to have fun on these forums and it is not the first forum I go on.