Jesuslightoftheworld
The world has nothing to offer us!
Jeffrey Dahmer converted to Christianity and became rather docile in prison, he had to be escorted by guards. Even before he was caught, he had a hard time coping with his horrible actions and struggled with committing murder. He still did it, but it wasn't easy for him.
Most serial killers struggle with homicidal idealization, and in many cases that homicidal ideation comes from pathologically externalized suicidal thoughts. In Dahmer's case, he tried to keep his victims alive on numerous occasions; he was just deathly afraid of being alone and abandoned.
I'm not sure if he could have been rehabilitated, or if the outcome would have been different if his pathology was treated before he went down the path he took, but we'll never know that because he was murdered in prison by another inmate. I do know that most people who are scorned as too hard-hearted to reach aren't always, and that scorn has made it harder to treat people with stigmatized mental illnesses such as B-cluster personality disorders.
I'm not saying there isn't anyone that matches your description, but I don't think humans are very good at judging who is beyond saving and who isn't. Who do you think should make that judgment call, and how many unnecessary deaths are you willing to risk for that?
Once in a great while, I wonder how God feels about Adolf Hitler. But what I know to be true about God is that He him too. But had no problem letting him burn in hell!