The Legend of Korra, Season 3

Korra:
(struggling frantically) When I get out of here, none of you will survive!

Zaheer:
You won't get out, unless the Metal Clan taught you a way to bend platinum. Once we administer this poison, your body will naturally react, forcing you into the Avatar State, in an effort to keep you alive. Sadly for you, you'll be entering it for the last time.

Korra:
(shocked) No! The Avatar Cycle-

Zaheer:
Yes. When we dispatch you in the Avatar State, the cycle will end. (glances at the other members of the Red Lotus) So we lucky few, this band of brothers and sisters in anarchy, are witnessing the beginning of an era of true freedom. Together, we will forge a world without Kings and Queens- without borders or nations. Where Man's only allegiance is to himself, and those he loves. We will return to the true balance... of natural order. And though you will never again be re-born, your name will echo throughout history: Korra, the last Avatar.