In a destructive cult there is a definite heirachy of power with a person or a group of people being in charge. You could definitely liken it to a dictatorship. The people on top are in control of everything. When new members are recruited they are not told what the group is really about, from the beginning. They may think they know what the group is about and what will be expected of them, but they do not.
Destructive cults are deceptive and manipulative.
They attempt to make people conform to being like the cult leader and their individuality is not encouraged. Many, many times cults twist scripture to use for their own gain. Some cults are called doomsday cults, and most of these are religious in nature. A cult would be defined as any group of people whose beliefs and rituals are not really mainstream. A cult would not be considered destructive if people can join the group freely with knowledge of what the group is really about, and if they can quit the group without fear or pressure.