If you had the power to enact a single law or overturn an exisiting law, what would it be?

i would like to make harsher punishments for rapist and murders. where i live a drug dealer just got 2 life sentences and a person that was involved with the shooting death of a 4 year old girl only got 15 years and a man that d four women only got 10 years i dont understand why there sentences were so short but they put a drug dealer away for life times 2.