Description:
My money’s on Starlight. She can self-levitate out of Amon’s bloodblending and attack at the same time, repel any close-range attacks with a force field, and vaporize Discord (the Elements of Harmony didn’t do this). By contrast, it only takes an exploding boat to kill Amon (a rocket launcher should also work just fine on him). Do the math.
Also, if you want to know who canonically won, just ask yourself: When was the last time they made a new episode of Avatar: The Legend of Korra?
