As you all have probably seen in the news, the Crips gang founder Tookie Wilson was executed for murders he was convicted of in 1979. Let's assume for a second that the death penalty is a proper punishment for his crimes. Many people felt that he should not be executed because of how his life had changed (because he seemingly completely abandoned his gang life and ties) and he had become a Nobel Peace Prize nominee for his anti-gang work and children's books.
So the argument (aside from the death penalty being inherently wrong) for commuting his sentence was: he has done a lot of good (and thus redeemed himself) and he still has a lot of good to do in his anti-gang work.
The courts saw no reasons to overturn the penalty because he was found guilty of the crimes and sentenced to the penalty with no apparent flaws in the trial or case. There was basically no judicial reason to prevent the sentence.
The Governator refused a stay because he had doubts about his convictions, primarily on the fact that he never showed much remorse: he never admitted to the killings (and hence showed no remorse for those crimes), as well as said little about gang violence and remorse for what he had caused and other crimes he had committed (although he did regret his founding of the Crips).
So we are left with the question: assuming that the good he has done and will do is enough to consider sparing his life, is remorse a necessary component? The Governator (and others) seemed to think so.
Here's another argument for sparing his life: Tookie himself said, "There is no part of me that existed then that exists now." While there is some part of that man that committed the crimes still with him, it does seem possible that he has changed enough so that the person who committed those crimes is no longer in existence. A new person, who emerged from the old one through gradual change, was the one executed.
Again, assuming that the penalty of death imposed on Tookie Wilson in 1979 was appropriate, was killing this man today justified or right?
(My very brief take on this: I don't think remorse is a necessary component, and because he still has good to do and is significantly different from the man who committed the crimes, a man was perhaps unjustly punished and it is likely that his staying alive would have caused more good than bad, so I think I'd fall on the side of keeping him alive.)
CORRECTION: Tookie's last name was Williams, not Wilson. His full name was Stanley Tookie Williams.