I agree with the death penalty in principle. In practice, I would only agree with it under the dictatorship of the proletariat because a bourgeois state should not have that amount of power.
I'm all for rehabilitative justice, but if it can be proven beyond any reasonable doubt that you:
intentionally murdered an innocent person
raped someone
molested a child
are a nazi
committed war crimes
then you have forfeited your right to be a part of society and should be removed from it. Imo there is no amount of re-education or rehabilitation that can fix a person who has done any of the aforementioned things.