Do your characters lead their own lives?
Is your star in their life’s prime
Or going through a period of strife?
Do they develop and change?
Do they have an emotional range?
The quickest way to kill a novel, script or short story is to populate it with flat characters. Flat as in no depth and in having “bland” reactions to the events depicted in the story. It sounds horrid but readers want to “see” the characters experience pain, laughter, learn from their mistakes, make mistakes to learn from in the first place and so on.
Do all of your characters fascinate you?
Can you see how their lives change for better or worse?
Are they fully rounded, believable too?
How do they affect others - by blessing or curse?
When I say fascinate, this doesn’t have to be in a good way. I’ve portrayed Brankaresh as a power hungry misogynist - do I have any sympathy with those views? Definitely not. I think out of all my characters it is easy to spot the one I really didn’t have any sympathy with at all and it was such a joy to kill him off!! Having said that I tried to get into the head of this wizard to find out how he could justify what he believes and what he does. And you need to do this for all your “stars”, whether they’re heroes or not. Readers have got to be able to see where your characters come that in that sense or they won’t be able to empathize. No empathy with at least one character (and it doesn’t matter if that empathy is limited) and you lose your readers.