What does one do with the irredeemable human?

Based on this Q, I am curious. Presupposing that we know the person is guilty of heinous acts, and should not be allowed contact with human society, what is to be done with them if capital punishment or other sure-fire killing methods, like General Population in prison, or putting them in any potentially fatal circumstance is off the table? A couple of people on that other Q stated that they strongly believe that killing such a person is wrong. So what’s to be done? Please, this is not a debate about the validity or moral value or not of capital punishment! This is about alternatives.