You can never 'match' the crime. Even if you go justicing around 'an eye for an eye' style, the perp will always have taken the initiative. You can never get that back. Everything you do is just a reaction.

That is what makes crime so heinous.

So your focus should be prevention at any cost first and foremost, then justice as prevention (= rehabilitation) as well. Murdering a murderer is pretty solid prevention though, I give you that.