When it comes to hero/villain team-ups, it takes a lot to bring arch-nemeses together. In the world of superhero comic books, team-ups were once main events reserved for special occasions, but now they happen every week. Heroes partnering up with other heroes is commonplace, and sometimes, the villains get in on the action and join forces to do evil. But only rarely do superheroes team up with supervillains - and they usually need an extremely good reason to do so.
Whether absolute evil villains like Red Skull or a world-ending threat like Thanos, there's always a bigger potential threat out there that can make hero and villain ignore their differences and pool resources for the greater good. Sometimes, it's the baddie who steps in to ensure that only they, and not some other chump, may slay their heroic archnemesis. Whatever the reason, hero/villain team-ups are always rife with tension; a “will they, won’t they” where the action in question is betraying their temporary ally.