Affleck is cast, Snyder and Cavill are in place, and there's even a tentative release date. Superman Vs Batman is happening, whether we like it or not. And while the internet has spent the past week or so going mad about Ben Affleck, or believing rumours about Bryan Cranston, some more pertinent issues have been thrown up. The main question that should be on every DC movie fan's mind right now should not be how to get Affleck to give up on the role in favour of someone supposedly more suitable, but rather the issue at the heart of this sequel's narrative: what makes Superman and Batman team up? The smart answer would be a threat that reaches beyond even the powers of Superman, and thus requires him to pick up the phone and dial into Batman's hot-line for a bit of support. A threat, for instance like Darkseid, or Mongul, or perhaps even Parasite, who would actually require the combined effort of two superheroes with different, but potentially compatible skillsets. Because, frankly, if we're treated to a sub-standard villain whose threat isn't immediately recognisable as larger than Superman's considerable powers, noone is going to believe that he would have any need for the perpetually miserable guy in black with a utility belt full of pretty gadgets.
Honourable Mention
A Bag Lady
In World's Finest #257, Batman and Superman combined to thwart the considerable threat of a bag lady with an alien in her handbag. Though it's highly unlikely to come to pass (or at least, you'd have to hope so, anyway,) even the merest suggestion that Superman vs Batman would follow this sort of thinking is just abominable. And while it's an extreme example, this sort of writing is precisely what needs to be avoided - inventing and overpowering a one-off villain with what is perceived to be enough of a threat to justify the super-team-up. In WF #257, the homeless bag lady in question was endowed with powers thanks to the gremlin living in her bag, who granted her every wish, which involved the destruction of Superman and Batman naturally, because bag ladies back then were less interested in building an army of cats, or frivolous things like not being homeless or insane.