According to a report from /Film, the ending for the Watchman movie differs from how it ends in the graphic novel. Did Zack Snyder change the ending? For more read the potential SPOILERS below.
“A couple of people who attended the screening posted reports on the IMDb message boards, only to have their posts quickly removed. Nothing has been officially confirmed, so PLEASE consider this with a grain of salt for now. According to the reports, the climax of the graphic novel where Veidt releases his squid in New York City, was not in the movie. Instead, Dr. Manhattan and Ozymandias build a machine that mimics Dr Manhattan’s powers and Ozy uses the machine to set off atomic bomb like explosions in various cities around the world.”