Basically, Earth-3 is like Star Trek's Mirror Universe, where heroes become villains and villains heroes. There seems to be some of that at work with the Arrowverse version of Earth-X.

With the villains of Earth-X, an alternate Earth in the DC multiverse in which Germany won World War II, attacking the heroes of the Arrowverse during this year’s November crossover event ...

DC officially canonizes Earth-27 as another memorable Elseworlds story — The Jurassic League. ... imagines the heroes and villains of the DC universe as gigantic dinosaurs.

With just under a week to go, The CW has released an official poster for the upcoming four-part "Crisis on Earth-X" crossover event, featuring a look at even more of the Earth-X baddies. Come take ...

DC Comics Psychic ape villain Grodd is back with a new Legion of Doom and a plan to conquer the Earth in new Justice League event We Are Yesterday: "Let's make it not Gorilla City, but Gorilla Planet" ...

In DC Comics' slate of "New 52" titles there's about to be nothing but villains as the universe finds its ... it's a team of villains," he said of the baddies from an alternate Earth.