A hidden villain in Batman v Superman

Batman v Superman: Dawn of Justice is about one year away from release (well, less than that – but it still feels one year away). So we can understand why some elements of the film have remained hidden. But it is all connected, as said.
In the trailer, we see Wonder Woman fighting an unknown character, in city which was already obliterated. From the start, we can say that this isn’t just a flashback, like the one of Bruce Wayne running towards the crumbling building.
And we also see her using her awesome bracelets to create a huge ball of fire/electricity/whatever that was. From this alone we can say that she isn’t fighting Superman – just like Batman isn’t fighting the Man of Steel when that awesome The Dark Knight Returns cover is adapted in the trailer (why would Superman use his lethal eye beams on a mere mortal?)
On the next page, the identity of the villain revealed!
