I think we all would like to believe there is goodness in everyone. Esav had SOME goodness in him in Kibud Av, but Halacha is that Esav sonei es Yaakov. I am sure that Adolph Hitler was all warm and fuzzy with Eva Braun, but if he were standing in front of me today…
Some people cannot be redeemed. Drug dealers on the street,addicts, pimps,gang members, these are members of society who do what they do because they WANT to.
Serial killers WANT to murder. It gives them pleasure to do so, and they often take trophies from their victims, so they can relive that pleasure over and over. There is no saving them. Only STOPPING them. Would you ask a shark to do teshuvah as it eat a swimmer in the ocean? It does that because THAT’S what it does! A psychopath or sociopath cannot do anything else. And for those who argue, keep them locked up, give them meds… well they can get pretty smart at NOT taking their meds, and why endanger other people around them, even if they ARE locked up. Can we say “Hannibal Lecter?” (Yes, I KNOW he is a fictional character, but there are such people in the world, Jeffrey Dahmer comes to mind). And who is to say they will STAY locked up????