K = Killer Instinct. Do your characters have this? Do you?! Firstly your characters, particularly your villains, need this (and often in the literal sense), but even the "goodies" need this to keep them going in the face of opposition etc. They need to know when to "go" for a course of action and it will be their instinct here that will ignite the spark which drives them on. As for you as a writer, do you have the killer instinct when it comes to editing your work? Will you take out anything that is really not working (and be open to the idea it isn't)? You need to learn to be ruthless about taking out anything that is not pushing your story on. The "kill your darlings" expression has a lot of truth behind it.
L = Learning and Laughter. Do your characters learn from their mistakes? A good story and great characters will have that as a major factor. Some of my favourite series novels have shown the lead character developing over time and I love that. It makes the character far more real to me. As for laughter, even in darker stories, there can be room for this. In the classic fairytales, for me, the Emperor's New Clothes is a great example of laughing at those who supposedly are superior but are taken in by conmen (and you do have to hand it to those tailors for sheer nerve). So where can laughter fit into your stories?