We know them and they suck... blood. At first they were us, but back up out of the grave. Then they were nobility living the high death. They've been powerful monsters and wimpy thugs. They've been heroes and vigilantes. They've been all kinds of things, including sparkly. It seems that inevitably they become not enough and then something else is required, something worse to put them on the defensive or to flip their role. Or maybe that something worse is just there to send them screaming into oblivion. Just what do you threaten vampires with or look to replace them with? There are some classic options.
Most modern vampires have as bad a time against hordes of zombies as anyone else.
Progenitors to modern vampires were more powerful and savage. When resurrected they quickly dominate.
Someone always turns up to make a better more efficiently and powerfully designed new vampire species.
Often unbeknownst to modern vampires they are a subspecies that are puppets and pawns of true vampires.
Werewolves frequently keep vampires in their place.
Magic is the great equaliser whether it be mages, devils, or otherworldly entities.
The melding of man and machine is a future nightmare of vampires both for feeding prospects and advanced vampire hunters.