There are some people beyond rehabilitation but I wouldn't say they make up the majority. But despite that, these are individuals who should not be let back into society under any circumstances. Individuals who even if you asked them that if you let them back into society despite best efforts, if they were given the chance to commit their crime again, they state they would because even they realize the danger they present to society. This includes pedophiles, serial rapists, and serial murders. Peoples who have a biological imperative or malfunction that makes it where they have to commit a crime to satisfy a biological urge, usually sexual.
Until think pieces such as this can address that without hand-waving and glossing over it, prison is necessary.
Tell me how you'd rehabilitate people like in this link and fix the root cause of their issues at the ages they committed their crimes
https://www.thecoli.com/threads/the...he-most-evil-murderers-ive-read-about.552622/