Looking back over the history of comics, it's very obvious that publishers like nothing more than f*cking with their loyal readers and that their favourite weapon in that war is the rug-pull plot twist. Characters are killed and revived, heroes are revealed to be deeply embedded villain agents and any comfortable expectation that can be messed with absolutely is.
Shock is a great currency to sell titles (and generate fan-propelled community marketing), and creators perpetually seem intent on smashing legacies and lore with unexpected turns and misdirects every couple of months. The fact that big screen adaptations of those stories would be similarly obsessed with twists should come as no surprise.
Since the beginning of the modern bubble of comic book movies, the sub-genre has been littered with crazy twists taking the wind out of audiences, both in terms of unexpected but satisfying story pay-offs and the kind of WTF moments that make sure viewers talk about them for years afterwards.
But which are the most effective and most shocking examples?
Though it didn't make it into the comparatively disastrous Amazing Spider-Man sequel - thankfully, some might say - the final twist that would have revealed a sting to the "who were his parents, really" thread would definitely have been shocking.
It would also have been poor, manipulative writing, which completely changed the make-up of Peter Parker as a character (since he's pretty much fundamentally SUPPOSED to not have a father figure), but that wouldn't have taken away the shock factor.