There was this mother and stepfather, they had an autistic son. I don't know how badly autistic but he was on his way to university so he must have been at least somewhat functional to start with. For some reason they just didn't want him to leave.
So they locked him up. They beat him, starved him, left him sitting in his own feces in a basement for months. When the police found him he was afew days off of death, the hospital staff estimated he had been fed on a couple of hundred calories a day.
Now, for me the explanation would be pretty simple. Mental illness caused by traumatic experience, by some sort of genetic defect or an unfortunate combination of the two. No evil, just a sad waste brought to you by the misfiring of mother natures meaner impulses.
But for you? Well you have abit of a problem on your hands with this. Because the "evil" can never be removed. It happened. Thats a man who will never be the same. Hes going to know for the rest of his life that his family viewed him as an animal to be tortured, nothing more. Theres no "I got the bad guy, now everythings fine." Thats not how life works.
And what of the couple themselves? Were they created "evil"? Well then how could they be "good"? Thats like me purposefully infecting someone with malaria then demanding they become healthy.
If its part of a plan then it can be nothing more than suffering for sufferings sake.