Katara: Now that I know he’s out there… now that I know we can find him, I feel like I have no choice. [“The Southern Raiders”]
Aang: I guess I don’t have a choice, Momo. I have to kill the Fire Lord. [“Sozin’s Comet, Part 2: The Old Masters”]
and then they both realize that they do have a choice:
[ID: Two matching gifs of Katara and Aang from “The Southern Raiders” and “Sozin’s Comet, Part 4: Avatar Aang,” respectively. They are making the same circular motion to attack Yon Rha and Ozai as their opponents cower in fear. Their attack then liquefies as they choose to hold back, drenching Yon Rha and Ozai in water. Katara and Aang then move backwards simultaneously as they relax their fighting stances. End ID]
