Korra, possibly, but one glimpse of her by anyone and it'd be all over the news. Since we know the drug can burn out the minds of its users, I think it more likely they did it to themselves, thereby making the waterbender Triad's plan a complete success.

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this world created by the
hands of the gods
everything is false
everything is a LIE
the final days have come
now
let everything be destroyed

--mu