A positive hero without a negative one is like an ignition without a spark. Often people root for good and at the same time empathize with evil. Perhaps they are pleased to realize someone is less than perfect for them. Sometimes the audience finds something in common with the character and unintentionally feels for him or makes excuses for him. The types of bandits are diverse, as is the public. Someone can not stand Hannibal Lecter, someone wants to see Darth Vader at the bottom of our list. But even a desperate "warrior of darkness" is capable of good or inclined to change.