1) Darkseid
Here’s the character who makes the most sense above all others to cameo in Justice League. It’s been confirmed for a while now that Darkseid would be held back for this first team-up movie before making his presence felt in the second Justice League film. As such, the central villain here will be Darkseid’s general, Steppenwolf.
Still, there’s very little chance that the Lord of Apokolips won’t appear in some capacity. We can’t help but think of The Avengers, and how Thanos showed up at the end of that movie. Obviously, DC doesn’t want to simply copy Marvel, but that’s the level of inter-connectivity and foreshadowing we’re used to in our superhero movies nowadays. For Darkseid not to show up at all would be a big letdown.
Certain sources have stated that Darkseid will be seen but not heard in Snyder’s film. Presumably, then, he’ll be pulling the strings in the background and the reveal of the big, blue bad guy in the stony flesh will be held back until future movies. Sounds good to us. Though we wouldn’t mind if that other rumour about Jeff Bridges already being cast in the role came true, either.