Ok, so I watched the Avatar origin episodes...
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I thought it was going to be a letdown, but it was alright. Not great, but I mostly liked everything about it. Except for the dark spirit part. It reminded me of Samurai Jack.
Long ago in a distant land, I, Vaatu, the shape-shifting Master of Darkness, unleashed an unspeakable evil! But a foolish human warrior who mastered the four elements stepped forth to oppose me. Before the final blow was struck, I tore open a portal in time and flung him into the future, where my evil is law! Now the fool seeks to return to the past, and undo the future that is Avatar: The Legend Of Korra!
The spirit can die when the force that's crushing it is great enough. By raining bullets down on the silent faces, already turned away from the world, you thought you could destroy the face of our truth. But we have faith in a different force. That hopeless hope is what sustains us now. My comrades are more numerous than your bullets, and more patient than your executioners.