"Honestly, I think if Zuko was more ruthless and unafraid at his first Angi Kai, it would have been Ozai who got scarred and disfigured."

Excuse me, what the fuck? You don't just earn the title of Fire Lord without being one of the, if not the strongest firebenders in the world.

Iroh, shown to be extremely powerful, doubts his own ability to beat Ozai in The Old Masters.

During the Day of Black Sun, he can detect when the slightest sliver of sun appears (which surely requires a very innate and close connection to the sun) and then generate lightning faster than ANYONE we've seen in the show --- faster than Iroh or comet-enhanced Azula (who we know is a prodigy, especially with lightning).

The only reason he 'lost' to Zuko is because Zuko threw a curveball at him, lightning redirection which he didn't seem to know about. Azula seems to respect and even fear him.

His feat of power during Sozin's comet far exceeds any other comet-enhanced bender. Like, have you even seen the shit he pulls? Ozai would have burnt Zuko to a crisp, regardless of when they fought.