Are your heroine/hero and villain related? Closely? Are they, in fact, siblings or, maybe, parent & child? Because if they are, you’re going to have a lot of trouble explaining your idea of parenting.
Do your characters care about the dilemma you’ve given them? Passionately? Desperately? Enough to carry both them and your reader through 72,000 words on the edge of their seats? Or are they actually thinking about that ticket they booked to Bermuda back last winter before they read up on the hurricane season and wondering whether they can sell it on eBay when the time comes. . .and maybe even make a killing. . .wait—who are you, and why are you so annoying?
How many of them are there? Do you even know? Proust put over 2,000 people into Remembrance of Things Past. Guess what? Nobody can name them. Nobody remembers what they’re there for. Nobody knows what was important to them and why it matters to anyone. This is why nobody’s read all seven volumes. (Except a small but elite cadre in San Francisco who hold a Proust Wake every year, most of whom actually lie about whether or not they’ve read his work, themselves.)
Do you like your protagonist? A lot? A WHOLE LOT? Almost infinitely? Because you’re stuck with them almost infinitely longer than your reader is. Agatha Christie grew to hate Poirot, just as Conan Doyle got tired to death of Sherlock Holmes, but they made the huge blunder of being popular authors and got stuck with them forever. Don’t make the same mistake.
Can your characters recognize the dividing line between likeably inept and sadly hopeless? between hilariously dark and simply unpleasant? between intriguingly naive and boring? Because your reader can.
How many facets do your characters have and what distinguishes them from each other? ANYTHING?
Which ones are just entertaining duplicates of each other? How are you going to merge them into single individuals with a lot of contrasting traits that make a weird kind of sense when they’re all put together?
Which ones are dull as ditch-water? Uh-huh.
Do your characters have the foggiest idea what they’re doing in your book? Or are they just sitting around waiting for you to enlighten them? Are they going to do anything about it when you do? Or are they going to pat their yawns and goggle at you politely?
When they talk, do they say interesting things? Because if they don’t, don’t let them talk. I mean it.
Do they have imaginative ideas about how to handle trouble and strife? Do they have the cojones to follow through on them? When trapped beneath a falling elevator, will they scream and bang helplessly on the walls, go into a fetal position, have a bad underwear day, or grab the upward cable and be yanked, yodeling like Tarzan, skyward and through a conveniently cracked door? Or will they, in a bizarre but inevitable twist, suffer a cosmic visitation that will have your reader looking askance at elevator shafts for the rest of their natural born days?
What the hell do your characters NEED? Because if you don’t know this, you don’t have a story at all.
Finally, is your villain really your heroine/hero? Yeah—I know. Caught you with your pants down, didn’t they? Again.