Humans differ from bacteria only in size and the ability to spout daft ideas! Retribution being among the daftest.

If you steal from somebody, you should work without wages until you have 'earned' enough to replace the cash or items stolen. For other crimes, instead of long sentences in the current prison system, I advocate either intensive therapy (if the offender would benefit), or short sentences under a total isolation regime (perhaps even shorter ones in sensory deprivation), with the option of therapy upon release.

As to murder, that's a complex matter. The 'crime of passion' warrants counselling and therapy, and is anyway liable to be a one-off. Self-defence likewise. Child murder, murder for hire, planned and premeditated murder, political assassination, terrorism, mass murder and serial murder all call for assisted suicide or involuntary euthanasia. Simply because the perpetrators are so damaged that they will always be dangerous, and because life imprisonment is far less humane, in the long run.

Idealism is a wonderful thing, it points out directions and destinations for us. But getting there and staying there demand a degree of pragmatism.