Aang’s conflict over his role as the avatar was never really resolved because he just got some bullshit magic macguffin right at the end that spared him from having to make a choice.

Removing the Firelord's power is a choice. He became the worst thing imaginable to him.

If Aang had come to the fight still conflicted over killing Ozai, and therefore still conflicted about his role as avatar, and during the fighting he had had a personal epiphany that in turn allowed him to defeat Ozai, without killing him, it would have been better, I think. Instead, the only thing that stopped him from instantly winning the fight was that he had a bad back, and with some helpful chiropracty from Ozai he was able to overcome that.

He was conflicted, his near death experience - the scarring from Azula's lightning had fucked up his chi pathways. He refused to fight and behaved in a defensive manner and his back was literally between a rock and a hard place and he was jarred into his full power. The entire cosmos and his predecessors going ":lets-fucking-go:"

I fucking love that show so much lol