it's chaotic here

The main problem

Because on one hand he did horrible things to everyone to which even his line goes way back to the early days of Avatar to which almost all of Aang's past literally said to kill him and that justice does deserve

Even Yangchen who was a fellow airbender said to do anything means necessary to save the world and she too was raised by monks

But to Aang to be told by the world even by his past lives to be with the world or against it because of his own beliefs and how he was raised (let's be honest here though probably even Gyatso would have said it too) he just couldn't do the deed

And I get people's arguments for this but killing is something that isn't so easily come by and I think that's the point especially within Aang's environment way of seeing that every life is sacred even the ones who does did unspeakable horrendous deeds of acts that Aang will never forgive

Just because one can forgive doesn't mean one forgets and the fact that Aang was able to find another way around without taking a life because of his beliefs...this is where I am at a lost because of not fully agreeing to which Aang should have killed Ozai