Warning: Takes place shortly after The Puppet Master and contains spoilers.
When with her friends, Katara promised forcefully that she would never, ever use bloodbending. It just wasn't within her to use such a horrific power. To rob someone of their own free will, to capture their own blood with her bending and force them to do her bidding…it was too horrific to even consider, let alone actually plan and plot and fathom.
But alone, curled up, hugging her knees to her chest with her eyes shut, she shuddered. Not just from the horror of the events that she had witnessed, but from its results.
The power that had filled her was intoxicating. The moment she had seized control of Hama, while her heart was stuttering and her guts her clenching in dismay and horror from the reality of what she was doing, her blood, her head, and the source of her bending actually sang.
This is what it means to be a master, was what she thought without control. The ability to rob a person of their very will, to make them your playthings…this is what it means to be the master of your craft…
And if she admitted it to herself, even though the tears stained her cheeks and she felt like she was going to throw up, she had to admit that it had felt good. It felt warm, and triumphant. It felt like she could do anything, even at the expense of her victims.
Bloodbending scared her enough with the very concept and idea of it. But what terrified her, really and truly terrified her, was how easy it was, and how good it felt, and worst of all, how good she was at it.
Out of all of the battles that she had faced, and would later face, the hardest one would be the constant one that she would have to fight within herself: the battle to ensure that bloodbending would never, ever be used again.
But she would fail. Grief has no morals, no boundaries. There are no ethics in a broken heart.