Avatar
Korra looks badass and can use all the elements by herself. The Planeteers have to work together just for the same effect. And Captain Planet? Pah! By the time they try to summon him with their sissy magic they'd already be dead. Not to mention he couldn't stop Korra unless she was polluting or harming the earth in some other fashion which, as the Avatar, she wouldn't do. Avatar wins!
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Thanks Drak - http://img.imgcake.com/drakeryn/genesissagajpgat.jpg
You're such a kid! By fr0q. - http://img.imgcake.com/genirisjpgde.jpg