Severe punishments don't actually help in the vast majority of wrong doing. Its been shown in basic upbringing, hitting your child actually makes them more violent over time.

Preventive measures don't work, mostly because they don't address the conditions that induce these violent actions. Many felons are impoverished or poor people who had no legal way out, or had very few options. Many are either formerly abandoned children or abused children with no safety net for the mental or physical health.

And then when they leave prison, their records follow them everywhere. They're permanently, they are scared in physical, mental and bureaucratic ways.

To your point, sure there are some people that we could define as true evil, but I would rather they be treated as the exception rather than the assumptive rule of all criminals.