As a legend Robin Hood represents the kind of principled nonconformist on which many heroes are based. We love to read about people who confront government wrong-doing even in a criminal manner as he did. But, if a similar character existed in real life, he would not be any more popular than a government agency attempting to redistribute our wealth. The majority of people would probably condemn him.
Rumpelstiltskin is an excellent fairytale that could be rewritten from the opposite viewpoint. Many characters on the poor peasant girl’s side seem as bad as the deformed old man who knows how to spin gold. The braggart father and the irrationally demanding king are the real villains who need to be defeated by the end of the story. But, they live happily ever after.
How do you parry the strength of the protagonist against the antagonist in a plot? Common wisdom says that the strength of the hero and villain need to be similar in order for the conflict to engage the readers. Therefore, authors create increasingly strong and vicious villains with the idea of making the protagonist look larger than life.
We only have to look at the very popular superhero comics and movies to see this occurring. A clean cut honest good guy hero like Superman comes from a wholesome family background and normally chases villains who are mildly destructive, maybe they want to spend their money to buy themselves power, but they are not trying to destroy humanity. Lex Luthor is nowhere as depraved as the Joker. But, the hero that must defeat the Joker is Batman, a vigilante with a vendetta and not necessarily a law abiding citizen.
Speaking of vendettas consider “V” the strange protagonist who conceals himself behind a Guy Fawkes mask. He is one of the most questionable anti-heroes. He does have the challenge of bringing down leaders of a corrupt society, but he has similar terroristic qualities to the person behind whose mask that he hides. “V” goes so far as to temporarily imprison the heroine. She must have a taste of the struggles that formed him to ensure she won’t turn him in to the corrupt authorities.
Compare “V” to the antagonist of Les Miserables. The police inspector is not a corrupt person. However, he believes he is chasing a criminal, perhaps a vicious one. When the villain realizes his error he destroys himself. The hero of the story, Jean Valjean, never raises a hand against him.
My conclusion? Be careful with creating a great evil to make your hero shine. Heroes are similar in strengths to villains and one of these is morality. So a hero chasing a very depraved villain is more likely to cut corners and break laws in order to catch that bad guy. The ideas that mold a more evil antagonist will often result in a hero bending our ideas of what is right. The hero will shine dimly as morally gray, or not shine at all.