I say Ares. When Diana goes to America as the Themysciran ambassadore, Ares, unknown to Diana, tags along and sets up shop in the U.S., posing as (or possessing) a military industrialist. Or maybe a U.S. general. Or maybe both. Anyway, he starts manipulating events to get a pretty ****ing massive war started. As in, WWIII. When Diana's somewhat unique brand of activism starts to irk not only Ares but also the United States Government. Ares uses the feds to eliminate Diana, as he's still too weak to take her out himself. As the clock conts down to armageddon and Ares' power grows, Diana has to battle against the United States army and eventually Ares himself to save the world from it's own corruption. Yes, it's an anti war allagory. So what? Wonder Woman is sometimes used as an allagory for major political issues. Hell, they could make it even more of an allagory if they mention the fact that, in the DCU at least, gods are an extension of humanity, instead of the other way around. So, while Ares is behind all of this, in the end it's our own damn fault since we created him through our glorification of war in the first place.