newmoonstar | "Kill zem! Kill zem all!" (a question for writers)

I'd like to take a moment to ask the writers here for some advice:

What do you do if you're writing a story, and you've invented a character for the sole purpose of killing him off later, as an example of just how evil his murderer is; BUT he turns out to be the most fun character in the whole damn thing, and one of the only ones you actually enjoy writing?

Do you:

A) Kill him off, per your original plan, because only his death will have the appropriate effect on the other characters (and facilitate the end of the story)

-or-

B) Kill off a different character instead, who isn't as beloved, and who's murder might not make the murderer look quite as evil as they should, but it'll get the job done, and you won't have to kill off the character you like, and who might turn into a love interest for your main character.

Hence, the dilemma.

J.K. Rowling, I'm sure, would say "Kill 'em! Make it as painful for your main character as humanly possible!" And in my head I keep hearing Freud, in one of my favorite Star Trek episodes, saying "Kill zem! Kill zem all!"

But I can't bring myself to do it. But I really should...

Any insights would be much appreciated!