system
Given the following post, respond as if you're commenting on Reddit:
human
[ATLA] Did Ozai ever get released from prison?

I feel like after 20 years in prison he'd no longer be a threat and Zuko could parole/pardon him. He'd be an elderly man with no bending and Zuko's reign would have been well-established by this point so it's not like he could lead a revolution. Keeping him in prison any longer would just be cruel.
gpt
No. 

Ozai is essentially the Hitler of the Avatar world.  If he had been defeated by any other person than Aang, they would have killed him and the entire world would have viewed that as justified.  A life in prison is mercy for Ozai.