The ben 10 one is Alien X, with the power of omnipotence.
It's established as being able to recreate the universe as well as surviving having the entire universe destroyed around it.

It's weakness is that it contains 3 distinct personalities including his own, that all need to be in total agreement in order to do anything, lest they just stand in place.

…To be fair, Aang doesn't fully master the Avatar State until the end of the series, and Deku is only able to go fully 100% because he has Eri on his back reverting his broken self over and over

I don't know about Ben 10 but those are rather situational cases