I think only David is in the same class. He is a textbook case of an attachment disordered child (the childhood condition leading to becoming a psychopath) complete with the reasons for his problems (abandonment by mother, unfeeling father). The fact that his character was written as it was is just amazing. And David Henesy is a wonderful actor, he almost always has his lines perfect AND he gives a subtle, multilayered performance than many adults could learn from.
Rhoda's lack of conscience and homicidal behavior defied any explanation other than genetics. She proved irredeemable. Therefore, she would outdo our little David. Thankfully, he WAS redeemable. It would have been difficult to have his role continue as it began. AND they chose to keep it realistic enough that he didn't become a well behaved child, just one that stopped trying to kill his father. Until being possessed, of course!