I was just wondering how devestating Kyubi could be if it wasn't a kindhearted person like Naruto who had Kyubi in him/her.

Take Gaara for example; if he had Kyubi, i think he would be even more of an asshole than he already is. He would without a doubt use it's powers to it's limits. And with evil intent as Kyubi has it's own mind, it would be some awsome power. And it would not be a happy life for a lot of people since the third Hokage is an old man and couldn't beat an insect. Sure Gaara has powers, but they are focused on him, and he uses it with not very wide range.

I think they all in the world of Naruto should thank their lucky star Naruto isn't a badass who feels like taking revenge on everyone who has treated him bad (everyone).