Brainiac

Although he hasn’t yet been confirmed to appear, it is strongly expected that Brainiac will be the first villain that the DCEU Justice League will face off against as a collective.

He’ll also represent the first non-Kryptonian alien threat, which will alert the people of the DCEU to the existence of an even wider universe, which could in turn result in mass panic – look at the impact that Superman and General Zod’s fight is set to have in next year’s Batman v Superman: Dawn of Justice.

He may actually be the reason the Justice League actually form. Batman v Superman: Dawn of Justice will lay the foundations, but the threat posed by Brainiac could be the reason they officially come together as a team.

Moreover, he has the ability to tap into the world’s technology. His impact on the Earth could be massive, therefore. He may even control every device on the planet or shrink some of Earth’s cities to tiny sizes, such is the level of his power.