Arkady Ivanovitch Svidrigaïlov
Svidrigaïlov is, arguably, the biggest bad-guy in the book. He makes Raskolnikov look like a saint. He's completely unfaithful to his wife, sleeps with his servants, and even attempts to rape Dounia. Before he kills himself, we learn that he's definitely a child molester and particularly fond of very young girls, one of whom he drove to suicide.
He's not alone. There are lots of mini-Svidrigaïlovs running around St. Petersburg. That's why Raskolnikov called that sketchy man in the park a "Svidrigaïlov." This man is really hard to read about and very easy to dislike.
Before he commits suicide, Svidrigaïlov shows some uncharacteristic acts of kindness. He convinces Sonia to take a big chunk of change to help her and Raskolnikov get along in Siberia. He's also nice to her and actually doesn't take advantage of her (as far as we know). Additionally, he arranged a place for her brothers and sisters to stay.
But that's where things get hairy. Would you trust Svidrigaïlov to find a home for your little brothers and sisters? Sonia did approve the matter, so we can only hope they are in safe hands and that he didn't give them to people he knew would hurt them.
The point is, Svidrigaïlov has done a few good deeds, but many more monstrous ones. Does he, like Raskolnikov, have a chance for redemption? Can you make up for bad things you do in the past? Does Crime and Punishment imply that there some crimes that can't be atoned? Does the novel suggest that child molestation is a worse crime than murder?