As you experience things in life, you learn and change because of them. This happens to the best book characters, too. Great books have character development...but there’s no rule that your character always has to improve as a person. Sometimes, characters end up growing backwards before they can start moving forward.
As an author, it’s your job to put your characters through awful situations. Give them what they want and take it away. Make them fall and hurt themselves at the wrong time. Reveal a terrible betrayal. Some characters take in all this badness and become better people because of it. But, some don’t. People don’t always improve through life. Some of them pick up more flaws as they go along. This is what I like to call growing backwards. It can be a lot of fun to write, if you can make your readers hang around to read it.
There’s something a little fun about a character who does the wrong thing. Extremely flawed characters remind us readers of ourselves. Most people are their own harshest critic. We can see the flaws in ourselves and find things to dislike. So a character who has some of these same negative traits becomes easy to relate to. And I personally have found that I like a flawed character much more than a perfect one. But when you’re making your character pick up new flaws along the way, you’ve got to be careful about how bad they become.
We’re all trained to root for the good guy to win, most of the time. If your main character becomes too unlikable, readers aren’t going to root for them and they may not hang around the finish the rest of the story. So be careful when characters are growing backwards. Let them be flawed and make mistakes, but don’t allow them to become evil in the eyes of the reader.
Because eventually, your character is going to have to learn from some of those mistakes. Your character is going to have to face what they’ve done and at some point, hopefully, become a better person for it. This is the big payoff of making a character grow backwards: there’s an eventual reward. Write it well, and your readers will reward you for your effort.