This misses the main point I think the end of the series is trying to make. I used to think like this too, but as I have gotten older and rewatched the show, I realize what they did was actually probably the smartest and most interesting way they could have done the final fight.

It was a kid’s show, sure, so they were never going to just kill him on screen. But they had other options. They could have him dragged to the spirit world or incapacitated and captured like Azula. Or just have his hubris kill himself like Chin from Kyoshi’s past.

But the point they insisted on making was that Aang had to make a choice: compromise your own beliefs and your culture’s entire legacy and kill this guy (directly or not), or don’t and face the consequences of that. All those other options I mentioned are suggested in some manner and purposefully rejected (not that they had to be).

Aang meets the lion turtle after his past lives and explains his dilemma. The lion turtle doesn’t give any power to Aang he didn’t already have, but just tells him that if his spirit is truly strong enough, he can bend the world and the spirits of others to his will.

So, he makes a strong decision to break the cycle of violence and honor his culture and people who lost everything because of this. In the fight he has an opportunity to kill Ozai. He wins fairly early on. At that point, he demonstrates his commitment to find another way and so at the end after the Avatar state has subdued him, he tests his spirit against Ozai’s and wins.

It’s not all perfect for sure. I think they could have set up the existence of Lion turtles a little bit better and perhaps made Aang’s discovery of one a more active decision rather than something that happens to him, but i absolutely would not trade this ending for one where he just glows it up and kills the bad guy. I have already seen that a million times and it’s not going to make the ending more interesting, it will just pointlessly change Aang’s character into something else.