I think the whole town, with the exception of a few (Giles Corey, Elizabeth Proctor and the wrongly accused), are all culpable because the lot of them conformed to the hysteria of the witch hunt. But if I had to pick three of the most responsible, I would start with Reverend Parris. He cares more about his own status than he does about the town’s welfare, the truth or the moral implications of his own actions. I’m reluctant to choose Abigail. She does instigate the entire string of lies which lead to the witch hunt. But her parents are dead and the only person who shows her affection is John Proctor; and this is doomed from the start. Abigail is one of those most responsible for the witch trials, but I personally hold more contempt for Parris and Deputy Governor Danforth. He is more concerned with the dignity and reputation of the court than he is about obtaining justice. His actions do not directly lead to the witch trials, but he has the ability to stop them and does not.
You have to blame those who started the witch scare but also those officials who perpetuated it and exponentially increased the hysteria.