Intimidation, in law, the illegal use of threats or violence to force a person to do or not to do a certain act. It includes false imprisonment, threats of injury to the person or members of his or her family, or actual violence. Generally, contracts made under intimidation have no legal standing.
What makes a person not only murder, but murder multiple people over days, weeks and even years? There's a special name for these types of murderers: serial killers.
With modern security, how can thieves walk out of a museum with millions of dollars worth of art? It usually just takes force and a little bravado.