It solves nothing, it heals nothing, it satisfies vengeance which many confuse for justice, it reconciles nothing, is irreversible, and is unjust.
Please provide your reasoning for calling it "unjust". I've read the whole thread (thus far) and haven't seen anything resembling a rationale behind your statement - only the assertion itself.
I decided to frame my inquiry based on the one tenet of your argument that is actually debatable in terms of logic - the "nothing" arguments are clearly opinion based on one's frame of reference, and the irreversible argument is irrefutable (but also immaterial).
Punishing a convicted criminal by death (whether or not he was in fact guilty of the crime convicted (irreversibility really does matter)) is unjust because 2000 years ago Jesus Christ took the full punishment on his body and died for that man’s crime. Being punished for a crime that has already been fully paid for is unjust.