In some ways, it’s simply the character himslf – his attributes as a villain. In the early episodes, there are plenty of examples of his petty sadism, and his childlike desire for retribution (consider when Patsy insults him on the radio, and his response to that) which becomes genuinely quite terrifying when he uses his powers to enact his every impulse. At the same time, though, David Tennant imbues him with a sense of charm and charisma – there’s almost a desire to like him. This is perhaps in part because he’s so well known as the Doctor; there’s time when I do think he channels his previous performance here, to great effect – the fact that we do, at times, like him and think he’s approaching normality makes the character far more insidious. In that way, then, he becomes an even more apt metaphor for rape culture, and the manner in which those sort of toxic attitudes are so pervasive, yet also hidden.
With everyone getting ready for Luke Cage, I thought it’d be a good time to look back on Jessica Jones, with an article about what made the odious Kilgrave such a fantastic character.
(I think I expressed the above poorly in places, particularly that bit about liking Kilgrave, because that’s not really the right way of putting it.)