It is the job of the writer to effectively build upon the "heart" of a character; that is, his goals, dreams and motivations that sometimes cause him to act in angelic or despicable ways.
Without acknowledging accurately a character's strengths you, as the author, will not be able to allow him to grow. This growth is never easy, and duplicates the challenges of life that your readers face every day. When writing a good character, though, you have complete, omnipotent power over him.
You choose the character's fate and the outcome of his efforts. You decide: will my character be noble? Will he be dramatic? Will he exhibit the characteristics of an ego-manic, or will he awake to know that a higher purpose awaits him if he will only pay attention to what life brings? Will he strive to overcome those hurdles that seem insurmountable? Will he go down roads less trodden by ordinary men?
Your character is multi-dimensional, like a faceted crystal, displaying its various properties, both good and bad. To be multi-dimensional, your beloved character is going to have to show the more negative aspects of himself, too.
As a character develops, so does interest in his welfare. Your readers are going to see themselves in them, or wish they we had equal tenacity. The character’s strength is what gives readers the courage to process their own demons and strive to see the best in themselves.