In DC Comics, there are a few words that are loaded with universe-shattering implications - "Infinite," "Identity," and especially "Crisis." At Warner Bros.' San Diego Comic Con Hall H presentation, DC Films dropped another loaded word when they made the announcement that their long-beleaguered movie about The Flash would be called Flashpoint. The very word "Flashpoint" is a Pandora's box of possibilities, both exciting and scary - Flashpoint was the 2011 DC Comics event that transitioned the original DC Universe into the rebooted New 52 universe.
Flashpoint coming to the DC Extended Universe has already sparked the debate within fandom of whether this means the DCEU will be rebooted or not. The DCEU has only been in existence since 2013 and has only produced four feature films, with the fifth, Justice League, bringing the DCEU's greatest superheroes together this November. It seems far too soon to even begin to be considering rebooting their movie universe, even if Flashpoint does make a speculated release date in 2020. Reboot or not, Flashpoint is its own separate universe with its own grim depiction of DC's world and its superheroes.
The core concept of any Flashpoint story - which The CW's third season of The Flash has already adapted - is Barry Allen time traveling and thus sparking the creation of a dark alternate timeline. Should the DCEU Flashpoint stick closely to the comics crossover event masterminded by DC Films President Geoff Johns, this means The Flash (Ezra Miller) would inadvertently create an apocalyptic version of the DCEU where the superheroes aren't mankind's saviors but are instead marching the world towards Armageddon. The two superheroes most responsible for the state of war gripping the world are Aquaman and Wonder Woman.
THE FLASHPOINT PARADOX
In the comics and in the DC Animation adaptation Justice League: The Flashpoint Paradox, the Justice League never existed in the Flashpoint universe. Instead, very different versions of the superheroes are forced to work together to prevent a war between Atlantis and the Amazons from destroying the world. In this alternate timeline, King Arthur of Atlantis and Princess Diana of Themyscira were lovers. The comics had them meeting in the ocean when he saved her from a kraken, after which they decided to marry and unify their two nations. At their wedding, rogue forces within Atlantis and the Amazons steadfastly against a Wonder Woman/Aquaman marriage conspired to assassinate Queen Hippolyta. With the Queen's murder, the two peoples were plunged into a war of attrition.
The Flashpoint Paradox cartoon changed the circumstances to be a bit more sordid: in creating a peace treaty, Wonder Woman and Aquaman began an affair, and they were caught by Arthur's wife Mera. Wonder Woman then murdered Mera (she would also kill Mera in the comics, but that would happen later in the story), and with that, Atlantis and Themyscira went to war. Europe pays the heaviest price in both versions of the story. After Atlantean forces destroy the island of Themyscira, Wonder Woman leads the Amazons to the United Kingdom, which they promptly conquer and make into their new home. Aquaman then attacks Western Europe and sinks it. Millions of innocent people die in the continuing conflict, including members of the Justice League when they intervene.