On a fundamental level, I oppose the death penalty. I also oppose "life without parole", because that in itself is a death sentence.
The death penalty (and again, life without parole) operates on a single, faulty assumption; that a person is incapable of change.
I don't believe that one bit. All other concerns regarding the death penalty become moot at that point, at least to me.
(Although I will say, killing to 'avenge' a death is not justice, it's just revenge, no matter how you slice it.)