Since he made his first entrance in the book, I'd say Van Helsing has showed signs of being good and being evil. "May I cut off the head of dead Miss Lucy"? (Pg. 217) This quote demonstrates both his evil side and his good side. When Helsing asks Lord Godalming this question, Arthur freaks out and gets angry for him even asking.
Helsing is really brave and strong for even being able to think about what he has to do, and that is a good quality. At the same time though you have to have some evil in you to be able to crush the heart of a vampire and decapitate it as well. As you can see, Helsing has some good qualities but he also is slightly evil too.
