I mean, everything about it was just perfect. It showed Iroh in his element (helping others through wisdom) and then it showed a very vulnerable side of him. The end almost brings me to tears, both for Lu Ten and Mako.
"Leaves from the vine, Falling, so slowly. Like fragile tiny shells, Drifting in the foam. Little soldier boy, Come marching home. Brave little soldier boy... Comes marching home."
Iroh singing that in tears just...it's perfect. Beautiful.