Why criminals don't deserve death

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I know that it also depends on how terrible their crime is. But please enlighten me why criminals don't deserve death. I personally don't find religious reasoning for not wanting a criminal to die is acceptable because it is almost as if you think that way because your religion told you so and have no thinking of your own. Although there are religious people who think killing a criminal is wrong based on their thinking not by religion. But I want to know why is it so. Wouldn't that be great if you wipe that awful criminal who destroy many innocent lives out of existence? If the criminal is gone wouldn't it prevent more lives from being destroyed?