TWOK Khan is the only compelling villain in any of the movies, which isn't surprising that they always try to recapture his shtick over and over. I always thought it was odd that the filmmakers resisted the temptation to hype up the film with the return of Khan. The whole John Harrison mystery box reveal served very little purpose beyond an attempt to surprise audiences (which it hardly did, let's be honest). The James Bond series made that silly mistake too trying to be coy about Christoph Waltz not being Blofeld, when everyone could see it a mile away. THE DARK KNIGHT and IRON MAN 3 did a much more effective job of hiding the revelation of their villains.
Though Bad Robot did drop the ball in not even bothering to claim Cumberbatch was Harrison the moment he was cast, which raised more eyebrows.
Though Bad Robot did drop the ball in not even bothering to claim Cumberbatch was Harrison the moment he was cast, which raised more eyebrows.