Iroh spends most of the first season playing the minion with an F in evil role to the hilt, up until the season finale when he
unsuccessfully attempts to stop Admiral Zhao from killing the Moon.
Then in season two,
he and Zuko are on the run and don't have many opportunities to do bad things.
In season three, he's
initially imprisoned by the Fire Lord, and then participates in the final battle on the side of Team Avatar.
I can only recall one specific instance in which he does something evil: Towards the end of the pilot, he and Zuko attempt to shoot down Appa with firebending, but Aang redirects it (and their ship ends up buried in the snow). Are there any other examples?
For an act to qualify as "evil," I expect it to meet these criteria:
- Iroh is directly and personally participating in the proximate act (e.g. "Iroh served Zuko tea on several occasions, and Zuko was a villain, so Iroh was aiding and abetting" -> no).
- The action is both intended and likely to harm a protagonist, innocent civilian, or otherwise "good" character (as Katara would put it, stealing from pirates doesn't count).
- The action is not in self-defense (escaping from and attacking the Earth Kingdom soldiers in "Winter Solstice" does not count).
- The action happens on-screen. His failed siege of Ba Sing Se does not count because we never saw it.