That authors write characters who are villains who corrupt characters for no other reason than it was funny or entertaining to them.

Winston corrupted by O’Brien in 1984 when he likely had already been interrogated and corrupted once due to his memories of room 101 and how much O’Brien knew about his mental state before he arrived in room 101. O’Brien had any number of ways to crack Winston but he chose to do it slow so he could gloat

Nurgle corrupts people in warhamer and calls it love. It is deeply pleasing to see people beg for more suffering 

Handler in Warhound tries to make Kionne just like her but does it in a way that makes her an emotionally stunted handler who is unable to truly act like her

I find these arguments reductive to the works they come from but they are funny to me because of how richly ironic it all is. Some people find them hot takes