How do your characters develop? Do they develop? (The lack of development can reveal a lot about a character in itself). Also development doesn’t necessarily have to be for the better. Bad experiences can make characters bitter. That in turn can affect their relationships but that character is still developing.
What does your character have to lose/gain? Is the stake high enough? How does your character cope with crises? Do they bring out the best or the worst?
Can you make use of your character’s memories to shape them? For instance, the Queen’s mother was murdered, obviously having a traumatic effect on the Queen and triggering her wish to keep her family close to her, no matter what it takes. That led to the Queen behaving in ways she would not normally have done.
Do your characters have friends? Could friends be useful for subplots (though note these still have to move your tale along and shouldn’t be a distraction or a device to get your word count up)? Can the friends guide your characters as to which route they should take? And friends can get it wrong, just as much as the main characters can by themselves. Best example of a good friend in my view is Sam Gamgee from The Lord of the Rings.
Do your characters have depth? Do they fall in love, hold grudges, take revenge? Do they develop say from wanting revenge to finding revenge wasn’t as satisfactory as they thought it might be? Can you see why your characters act the way they do?
Do you show why your characters are villainous? Is the reason good enough to keep the villainy going or can it be overcome? Do you show how your world works? What’s the system of government? Are there those who resent the way things are run?
Your characters’ main attributes should be evident through (a) what they say and (b) what they do. Having said that great fun can be had with hypocritical characters or those who don’t think they are hypocrites but everyone else around them knows differently! Eileen, for example, thinks hypocrisy is something that happens to other people! Do you like your characters? Can you see good points even in your villains?
Are there ambiguities in your world that frustrate your characters or that they can take advantage of? How does your world treat criminals?