stockholm/lima syndrome, with torture, human experimentation, loss of self/absolute obedience, and then gradual recovery while pretending to still be affected (largely because he's desperate for acknowledgement and the kidnapper adores him), with a pretty huge age gap.

a criminal trying to force a little runaway from the syndicate to fear/obey him, by taking him up a tower and letting him watch with binoculars, while he calls up the kid's younger friend, convinces him he's being watched and might be sniped if he doesn't follow orders, and culminating in public stripping in front of the glass doors of the building, to humiliate the boy and force his friend's compliance..

(the kicker being that the younger boy was sexually abused; the criminal didn't know it, but the boy's friend does).

in games, probably the time a murderer trapped starving dogs in a shed for days, to then throw in his animal-loving victim with them so they'd rip her apart, then cut off her fingers and burned them to lose the fingerprints (or that was the plan until her castmates got squeamish). he did it as part of a game to challenge the detectives there with figuring out who did it. because it was boring.

to be honest, I come up with scenarios tons worse in my head. it's just not usually stuff that'd fly in games and I don't get too many people to play with who are as interested.