Warning, Spoiler:
Zach Snyder's Watchmen—or, at least, the version recently screened (we'll get to that in a moment)—does not end as the novel did. In the film version two members of the group, Ozymandias and Dr. Manhattan, construct a device which mimics the superpowers of Dr. Manhattan, who attained his abilities in a nuclear explosion. Ozymandias then detonates the device, destroying several major cities, and frames Dr. Manhattan as a means to an end to attain the same desired result as the comic's original plot, that of global unity. As in the basis for the adaptation, the rest of the group remains silent about the real events that took place, believing that the overlying result is more important than the truth.