Sociologists looks for patterns in human behavior and in social institutions where a profile of pastoral and spiritual abuse will emerge. Abusive churches, past and present, are first and foremost characterized by strong, control-oriented leadership. These leaders use guilt, fear, and intimidation to manipulate members and keep them in line. Followers are led to think that there is no other church quite like theirs and that God has singled them out for special purposes. Other, more traditional evangelical churches are put down. Subjective experience is emphasized and dissent is discouraged. Many areas of member's lives are subject to scrutiny. Rules and legalism abound. People who don't follow rules or who threaten exposure are often dealt with harshly. Excommunication is common. For those who leave, the road back to normalcy is difficult.
...a group of people, which claiming to be Christian, embraces a particular doctrinal system taught by an individual leader, group of leaders, or organization, which (system) denies (either explicitly or implicitly) one or more of the central doctrines of the Christian faith as taught in the sixty-six books of the Bible.
Source: Alam Gomes, Cult: A Theological Definition, excerpt from "Unmasking The Cults"