Dominators

"That is not the name of a species that comes in peace."

- Wally West

The Dominators are a race of extra-terrestrial beings.

Earth One
In 1951, the Dominators landed on Earth, abducting humans to gather information about them. They attacked, killing hundreds of soldiers, before leaving the planet.

438 years later, the Dominators returned to Earth, prefaced with a warning to Earthly authorities that they meant no harm, though in fact planning war. Four ships crash landed, one of them in Central City, spilling forth with Dominators. This faction set up a mind control device in an old salt mine, but this device was eventually destroyed by Supergirl, with the help of The Flash.

Earth Thirty-Eight
Sometime before Kara Danvers was born, the Dominators traveled to Krypton and performed experiments on a number of people, as well as killing a lot more.

Powers

 * Super strength: The Dominators were said to be really strong, overpowering inhabitants of Krypton, although Kryptonians usually don't exhibit superhuman attributes under a red sun.
 * Telepathy: The Dominators are able to communicate telepathically with others, seemingly also being able to use their own language, despite languages such as English not being their native language.