Where do they fall on the scale?
That's a tough scale to exhibit. Heaven's Gate and Branch Davidians would be TEN in many books, but their membership was so small in comparison to JW's. JW's have 8 million or so members, but they haven't (yet) told the members to drink the Kool-Aid like they did at Jonestown.
I would have to say that everyone's scale will be different.
Many churches exert little control over the day-to-day lives of members. Cults like the JW's exert high control over that. They encourage shunning and withdrawing from normal "worldly" events and lifestyles. They wreck the future for many young ones, either through crushing their goals or through making them choose normalcy over family.
On my scale, JW's would be an EIGHT out of TEN. That leaves room for the real whacko killers and reincarnated messiahs to the NINE AND TEN portion, but also allows the Universalists and lower control groups below that number. But to be fair, I would put Muslims right up there at EIGHT also.