The severity of the punishment does not determine the severity of the offense?

I once heard someone point to a murderer and say that he is less bad than a Sabbath violator because his punishment is stoning, while they punished him with a whipping. So I think that the severity of the punishment does not determine the severity of the offense. What do you think? If we put aside murder because it is one of the most serious offenses, and we put, say, eating leaven or any other Sabbath prohibition against the Sabbath or anything that is punishable by stoning