The used rhetorical device is Hyperbole.
Saying that something is a billion times better is hyperbole because it is not really that much better, you would just be over exaggerating.
We can't have hero's without villains/monsters. So I AGREE. Because hero's are only hero's because of the fact of us having monsters. Who would they face? Nothing? Then they wouldn't be hero's. We need bad things /people to have HERO'S to save and help us otherwise if everything was perfect, we wouldn't need hero's.
It can identify your target audience
Creating an audience profile, you will be able to see the social and economic characteristics of your audience, that will allow you to identify your target audience.