There’s a quite nice little essay on the subject at, of all places, the Texarkana Gazette, which answers the question by comparing Tony Alamo’s cult with actual Christian churches.
The differences are nicely highlighted in this little snippet
“Where we see little oversight of a religious leader, often that leader will end up getting in trouble because there’s that lack of accountability”.
Accountability to persons other than oneself- that’s the key. If you belong to a congregation where the leader considers himself or herself above reproach and beyond question; if said leader leads with an iron fist and enforces his or her will on the group; then you can be fairly sure that leader is the leader of a cult.
And if you think back to all the cults in the news these last many years, you’ll see how true that is.