Justice League: Origin

This one is a no-brainer, if we take into account the fact that the DCEU will be built mainly upon the New 52 comics. Justice League: Origin, as the name suggests, shows the events which lead to the forming of the Justice League. If this story will be adapted, it will certainly skip the moments when the superheroes meet "“ we say that because this will happen during Batman v Superman.

However, all the other events could be adapted. Thus, the newly formed team will have no trouble with the scores of parademons sent to take over the world. However, they will find themselves at odds when the hidden mastermind appears: Darkseid himself, who cannot be hurt by any of the attacks of the separated superheroes.

Superman is abducted, Green Lantern is almost killed when trying to solo Darkseid, Flash can't do a thing, and so on. The only one who finds some sort of answer is Cyborg "“ so, after Batman saves the Man of Steel, Darkseid is sent back to Apokolips, not before swearing to return.

If the DCEU will adapt this storyline (and we don't see why it wouldn't), then this will be an action-fest like never before. And the best thing is that the heroes won't fight between them until the major threat is revealed "“ Batman and Superman will already be pals after the events of Dawn of Justice.