I get the same nervous tic whenever I read insipid Mary-Sues who get away with everything in the book. Bad characters defy the rules established and barely get a slap on the wrist, or worse, the rules suddenly change once the author realizes that the penalty might be too harsh for their precious character.
I’m pretty old school and I believe in spanking my kids (if I had any.) Though some parenting methods vary from person to person, the principle still applies. Kids need discipline—no slap on the wrist, or pansy-ass scolding, but hardcore reprimand.
Same rules apply to writing. You can’t let your character run around throwing tantrums, getting into shit, manipulating people, and NOT suffer the consequences for their actions. This is a sign of a very spoiled, unbelievable, and un-relatable character, in turn, a Bad Writer.
Don’t let your characters get what they want without earning it. Set distinct ground rules. If the character breaks these rules, no matter the reasoning or circumstances, there must be a consequence. Something must be taken away from them. It may seem harsh, but it is for the better good of the story. The character will grow, become well-rounded, and your authority as a storyteller will not be questioned.
Do not play favorites. You may have a character that you lean more toward, maybe they look or act like you, maybe they have part of your name. But no matter how cute they are, that shouldn’t stop you from whoopin’ that ass when they step out of line. NO character is above the law. Even the main character, the star of the show, must follow the rules you established. If you make it clear that something is forbidden and that A + B = C, then stick to your guns. And for god’s sake, don’t flip the script mid-story. (Deus Ex Machina)
Allowing your character to get away scot-free is not true to life and gives a false notion to the reader that it’s okay to act a fool without consequence. Like children, our characters will reflect us and how we govern the small world we operate. Just like a mother wouldn’t let their kid run around with dirty clothes and messy hair, a writer shouldn’t allow their characters to run amuck.
As the writer, you put your foot down, and allow your characters to deal with punishment. This will enrich the story and the character and add a creative maturity that can only come with correction and boundaries.