Book: The Half Blood Prince Dumbledore has just been betrayed by Professor Snape and even though readers weren't his biggest fan, that dislike has now turned into pure hatred. Up until this point you believed that Snape couldn't be trusted and you thought Dumbledore was a fool for defending him for all of those years; and now you've just been proven right. Snape has just taken out Harry's biggest ally and the only wizard powerful enough to evoke fear in Voldemort. It was this act of betrayal and disloyalty that shocked readers, but it also meant that if Dumbledore was gone, who was going to be next?