Character development is usually a good thing. If a story progresses without the characters changing at all, at best it is frustrating, and at worst it means that the characters are just thin wrappers around an ideology the author wanted to express.
Sometimes, however, character development goes badly. An example that comes to mind is in the 1Q84 series, where Aomame, a strong-willed and driven female character in the first two books, becomes a simpering dependent on Tengo, a male underappreciated author character, as soon as they meet up. It was such a radical shift in personality that I lost all interest in the book, and it was a struggle to finish it.
Do you have any examples of character development which went, in your opinion, badly? How would you have liked it to go? Did I just miss something about 1Q84 book three?
That's why you should have a structure when you do a good story. You should not just start writing and then create characters on the go. Stop. Sit down. Create one character. Digit his/her gender, age, phonotype (including it's usual clothes and accessories), personality (could use MBTI for practicality). Then start writing it's story in a chronological order. Create a story with this character, even if it's a simple story. Do it for the other main characters. Get all the structures and do something like a mind map. Then, when you start the main story structure (would be good use a mind map too to set the plot, the rhetorical methods, the basic "monomyth" thing), you can just go and insert the characters structure inside the main story structure, so you have a very rich type of storytelling, not just a unorganized piece of soykaf.
>>195 They did know each other as children, and lost contact, but when they met up Aomame effectively reverted to a child. Her entire personality became about Tengo. The strong person present in the first two books was just... gone.