WARNING: Spoilers for the end of Justice League ahead…
Justice League has two post-credit scenes, the first a bit of fun, and the second setting up a major villain for multiple future films.
The First Post-Credit Scene
Supes then jokes that Flash is off the team if he loses, and tells him he has to take the Justice League to brunch post-race.
And then they’re off. Though, like the end of Rocky III, we see the start of the concluding contest, but not the end. So it’s really more of a tease.
The Second Post-Credit Scene
This is the big one. And it starts in a prison, with a guard making his way towards Lex Luthor’s cell, saying, “Come on Luthor, let’s go.” But the bald figure in the cell has his back turned, and doesn’t move.
The guard follows that up with: “Alright, stop jerking around, Luthor, or I’m going to have to come in there.” The figure turns, and it isn’t Lex but rather a stooge standing in his place, laughing maniacally.
The action then cuts to a speedboat speeding to a yacht, carrying a figure that looks rather a lot like Deathstroke. Lex Luthor is on said yacht, and greets him by saying that he’s celebrating God’s return, “out of the ground, and back up into the sky.”
Luthor continues, “He and his odd little friends are forming some kind of league.”
“You better not be wasting my time,” barks Deathstroke, who by now we can see is played by a blond Joe Manganiello.
“No, I have too much to live for, and more important things to do,” comes the response. “We have to level the playing field, Mr. Wilson. To put it plainly, shouldn’t we have a league of our own?”
Who is Deathstroke?
Slade Wilson — aka Deathstroke — first appeared in New Teen Titans #2 in 1980. Created by Marv Wolfman and George Perez, he’s a mercenary and skilled assassin who has battled both the Justice League and Teen Titans.
As a gun-for-hire, he’s previously been a member of the Injustice League, Suicide Squad, Checkmate, H.I.V.E., Team 7 and the League of Assassins, the latter of which Luthor might be referring to in the aforementioned scene.
But it’s more likely Lex means the Secret Society of Super Villains, which Luthor set up in the comics, and of which Deathstroke was a founding member, alongside Talia al Ghul, Dr. Psycho, Black Adam and Calculator.
Eternal enemies of the Justice League, Darkseid was also involved with the SSoSV, meaning that the post-credit sting nicely lays the groundwork for a Justice League sequel in which he is the big bad.
But Deathstroke is also the villain in forthcoming standalone movie The Batman, which Matt Reeves will both write and direct, with production set to start soon.
So in effect, this brief scene sets up not one, but two movies.