After months of wondering who the main antagonist in Ben Affleck's Batman movie will be, the question seems to have finally been answered. Last week, after Affleck posted a video of a live action Deathstroke on social media, it was reported that Slade Wilson will be the primary villain in the Dark Knight's first DCEU solo movie. Although he's fought numerous heroes in the DC universe, Deathstroke has had a special feud with Batman for decades, so to see them finally battle each other in live action is an exciting prospect.
However, it's important to remember that for the most part (the Teen Titans cartoon and Arrow being some of the notable exceptions), Deathstroke isn't a scheming antagonist. He's certainly smart, but he's a mercenary, meaning that he works for whoever will pay him. So even though he'll give Batman a run for his money, it's likelier than not that he doesn't hold a personal grudge against the Caped Crusader. If that's the case, who has hired him to attack Batman in the solo movie. We have some candidates in mind...
The Penguin started out as a typical super villain committing crimes either on his own or with a gang, but in the modern era, he prefers to manage his illegal enterprises from the Iceberg Lounge, his "legitimate business." So although he's not unwilling to make an example of one of his minions if they fail him, usually with one of his gimmick umbrellas, he would prefer not to get his hands dirty fighting Batman himself. That's why he'd bring Deathstroke on board instead. After years of unsuccessfully trying to eliminate the Caped Crusader using his own manpower, Penguin decides to hire Slade Wilson to get the job done. Although a younger Oswald Cobblepot is one of Gotham's lead characters, it's been almost 25 years since we've seen Penguin properly battle Batman in live action. Now is a good time to bring in a new version of him, but with Deathstroke's involvement, it won't feel like retreading a story fans have already seen or read.
Like the modern Penguin, Black Mask is often used as more of a crime boss than a colorful super villain. Unlike Penguin, the Batman movie would be wise to introduce him as a new player in the Gotham underworld rather than someone who's been around a while. In a matter of months (maybe a year at most), he's worked his way to the top of the Gotham City criminal empire, and only Batman stands in his way. Enter Deathstroke, who Black Mask hires to get rid of the last obstacle towards him controlling the city's interests. Remember, Black Mask hired Joker to terminate Red Hood in Batman: Under the Red Hood (though that bit him in the ass), so it's not unreasonable for him to hire Deathstroke to take on the Dark Knight. Black Mask is also a formidable tactician and fighter on his own, so in the movie's climax, we could see him battle Batman personally when the vigilante finally breaks into the mob leader's stronghold.
Ra's al Ghul
At first, Ra's al Ghul hiring Deathstroke doesn't make much since. After all, The Demon's Head leads the League of Assassins, so he an army of killers at his disposal. However, in the 2000s, Deathstroke was notable for being the only freelance assassin the League employed in the comics world, as Talia al Ghul used him for a few missions. Deathstroke was also connected to Ra's al Ghul and the League in the animated movie Son of Batman, although in that story, he was a vengeful former follower carrying out revenge. Although Liam Neeson's Ra's al Ghul was a captivating character in Batman Begins, we have yet to see a truly faithful version of Ra's in the movies (or even on TV, if you didn't care for Arrow's version). It will take some mythos-bending, but if the Batman movie can come up with a plausible reason for why Ra's would send Deathstroke after Batman rather than one of his followers, then fans could get a cool story involving Batman fighting Deathstroke and Ra's. The latter battle would have to be with their shirts off, right?
Court of Owls
The Court of Owls are the youngest adversaries on this list in terms of when they debuted in the comics, but within the DC universe's own chronology, they've been active for centuries. Gotham City's wealthy and elite shrouding themselves in owl masks have manipulated events in Gotham City from the shadows, and until the start of the New 52, they were considered to be a myth. Whenever they've needed to turn the tide in their direction, they've used the Talons, undead assassins they keep on ice. For the Batman movie, however, perhaps the Court turn to Deathstroke first to eliminate Batman, as he's finally getting close to uncovering their existence. The Talons may be harder to control in this universe, thus necessitating that they only be used as a last resort. In the meantime, since the Court has more wealth than a third world nation, they can easily afford to pay Deathstroke for the job, but as talented as Slade Wilson is, he won't be able to stop Batman from coming face to face with the Court eventually.
Gotham and the Arkham video games have done a tremendous job adapting Hugo Strange outside of the comics, so now is the prime time to feature him in a movie. Strange was already a seedy character well before Batman hit the scene, but upon learning about the vigilante, Strange found himself obsessed with him. For the Batman movie, Strange's background in psychology, biology and chemistry needs to be retained, but having come to Gotham City, he decides that it's up to him to capture the Bat and study him for his own nefarious purposes. Of course, he can't accomplish this on his own, which is why he pays Deathstroke to find Batman and deliver him, as opposed to just gut him. From there, Strange learns that Bruce Wayne is Batman, and that's when the real trouble begins. Throw in some of Strange's trademark Monster Men or some other cruel experiment of his, and you have an amazingly insane Batman movie.
When Hush was introduced to the comics, he worked with the Riddler to manipulate many of Batman's most notorious enemies into attacking and even mentally screwing with the crimefighter. It was previously rumored that multiple Batman villains would appear in the movie, but even if that's no longer true, they could still loosely adapt the Hush story arc using only Deathstroke. After figuring out that Bruce Wayne is Batman, Tommy Elliot, also a man of significant means, hires Deathstroke to kill his rival, but unlike Slade Wilson's previous jobs, he's also supposed to psychologically torment his target, even though that isn't his style. For whatever reason, Deathstroke doesn't get the job done, leaving Tommy to don those facial bandages and become Hush. Granted, Hush has also trained his mind and body around the world, so he's a formidable match for the Dark Knight. Nevertheless, he'd prefer if he can twist his adversary around before seeing him die, which is why Deathstroke is sent out first. When that plan fails, Hush will take matter into his own hands.