Most of the time, Wonder Woman is one of the main heroes of the DC Universe, and she still stands as perhaps the most popular female superhero of all time. This has seen her have almost as many alternate universe incarnations as Superman and Batman, where she's been reinterpreted in countless ways across the Marvel Multiverse. One variant in particularly flipped the script entirely, turning Diana into a ruthless, vengeful killer in a world where the Flash's attempts to change the past broke the timeline.
The alternate universe of Geoff Johns, Andy Kubert, Sandra Hope and Alex Sinclair's Flashpoint turned Wonder Woman and the Amazons into heartless villains who waged a horrifying war against Man's World and Atlantis. This turn of events came about through conspiracy behind two empires, dooming the world at large to a remorseless regime and transforming the Amazon into a heartless conqueror.
Wonder Woman in Flashpoint
In this alternate world, a young princess Diana met fellow royalty Orin of Atlantis when she was attacked and poisoned by a Kraken. After he saved Diana's life, there was a brief truce between the similarly introverted Atlantis and Themyscira, a bond which was to be sealed by the marriage of Diana and Orin. During the interim, however, the first cracks of this tenuous relationship were formed through the future Aquaman's taking of a concubine in Mera.
Behind the scenes, Amazons Penthesilea and Artemis and Orin's brother Orm plotted to have this union ruined, in doing so throwing plans of integration with the outside world into turmoil. Artemis, gunning for Diana herself, threw an Atlantean trident that struck and killed Queen Hippolyta. She did so in the armor of Aquaman's ward Garth, and the murder was promptly blamed on the character who is Aqualad in mainstream continuity.
A latter attempt by Aquaman and the Atlanteans to circumvent an all-out war led to Themyscira's destruction, with the Amazons intent on showing their own power. The loss of their island home "at the hands of" the Atlanteans saw Diana finally become the Amazons' queen, with her first course of action being to find a new home.
Wonder Woman vs. Aquaman
Though her actions were initially based in vengeance and arguably justice, Wonder Woman's actions upon venturing to Man's World are truly evil. She and the Amazons take over Britain as a new Themyscira simply because they can, caring little for the many innocent lives lost. When Mera and other Atlanteans try to attack Diana and her new metahuman Female Furies, the result is Diana's beheading of Aquaman's wife and subsequent sporting of her former helmet as a warning.
Later on in the events of Flashpoint, Wonder Woman nonchalantly kills innocents such as Captain Thunder -- the Flashpoint Captain Marvel/Shazam! --and ironically Steve Trevor. This shows once and for all that Diana sees all those who stand in her way as mere pawns or roadblocks to be gotten rid of or ran through. She also falls back more on her warrior ways than her superpowers, favoring the sword to any Lasso of Truth. Her conquering mindset arguably makes her even more morally corrupt than the version of Wonder Woman from Injustice, who at least in her mind still had some moral compass guiding her actions in Superman's regime.
The Injustice Wonder Woman corrupted the ideals of the Amazons, whereas the Amazons in the world of Flashpoint had seemingly no such morals. They actively hate men and blame them for all of the world's ills, showing how they're far less tolerant and erudite than their mainstream counterparts. While the real Wonder Woman is a far kinder and more compassionate figure, but Flashpoint showed just how dangerous she would be if she ever broke bad.