How does Mr. Hyde's character develop during the story?

The correct answer is - His cruelty becomes increasingly deliberate.

Mr. Hyde is constantly battling between his two personalities - Mr. Hyde and Dr. Jekyll. When he is Hyde, he is a good man and a decent being. But when his other persona takes over, he becomes a monstrous being capable of doing anything. Well, over time, Hyde becomes stronger and stronger, and wants to commit various atrocities and almost nothing can stop him.