During my tumblr era, there was this cloud of "huh" over Kate and Ari. It gave off the possibility of a relationship. I don't know if people still get that impression or remember when that vibe hit, but I swear I'm not fucking crazy.
Anyway, my brain compared it to Hannibal and Clarice, which had two endings: the book, where they ran away together under false identities, and the movie, where Hannibal got away alone. Either way, she doesn't kill him, and he doesn't kill her because feelings.
Kate and Ari obviously ended the exact opposite way.
My assumption is that the reason Ari killed Kate was to inflict the most emotional damage upon Gibbs. We know there was some heavy hinting at Gibbs and Kate possibly becoming a thing, especially in season one. It got more into a family dynamic later.
But, Ari could have just killed Gibbs, but then Gibbs wouldn't have suffered enough. Tony had worked for Gibbs the longest at this point so one would think they were closer than Gibbs was with Kate... but Ari didn't see that. He saw Kate as the best target to hurt Gibbs.
I'm trying to think if anything similar happened in other fandoms. I know it's all down to real life with the writers combined with Sasha's decision to leave in the end, but Ari and Kate had such a vibe that, looking back, I'm surprised Kate was killed by Ari. They could've had Ari kidnap her, had her disappear, but instead they went with a sequence of events that I don't think I've seen before.
What other fandoms pulled a similar attraction dynamic between good guy/bad guy, and how did it ultimately end? With a fucked up "happily ever after" like the Hannibal novel, with simple separation and no giving in like in the film, or with one killing the other like with Ari and Kate? And if there's many of those instances, what was the vibe behind the death?