Brainiac or just Lex Luthor?

One older rumor said that the newly formed Justice League will have to face a galactic villain. In the form of Brainiac.

In Man of Steel, Zod and the Kryptonians were attracted to Earth by the beacon activated by mistake by Superman. Apparently, the same beacon is heard by Brainiac too. The villain, attracted by the prospect of finding Kryptonian technology, will arrive on Earth.

Another possibility is to actually have Lex Luthor as the baddie who unites the Justice League. He has the money to build whatever he wants, including his awesome mech suit, as well as for attracting other villains in an Injustice League.

There is, however, another possibility – check the next page!