Katara says that he didn't love their mother as much as she did on a grim, overcast evening.
She spits it out like a cornered animal, because he pushes her into a corner and refuses to back away. Her eyes are haunted- Jet's eyes, filled with hate of the Fire Nation, no room for anything else. Aang is leading a moral circle-jerk, preaching about forgiveness and two-headed rat vipers, but he has more practical concerns. If his sister goes out and ends the bastard's life, worthless as it might be, it will destroy her, send her spiraling down into a pit he doesn't think she'll escape from. He pulls the card that's sure to persuade her- it backfires spectacularly.
It wouldn't hurt so much if it wasn't true.
He isn't heartless- he cared deeply about Kya, of course, she was his mom. Only he wasn't the one who found her charred body in their tent after the invasion, didn't have her necklace draped around his throat. Katara stepped into her shoes seamlessly, taking over all of the work Gran-Gran was too feeble for, corralling the other tribeswomen when there was nobody else left to do it. He never asked if she struggled to shoulder the burden, never asked if she could use any help. She fussed and cooked and cleaned while he played at being a warrior, until he came to the sickening realization that he could no longer remember what his mother looked like.
Katara didn't forget, though. Katara can't forget. And he wonders, watching her take off on Appa, if he should be sitting beside her- a last apology, maybe, but he isn't sure who it should be directed towards.
