Too much mercy... often resulted in further crimes which were fatal to innocent victims who need not have been victims if justice had been put first and mercy second. ↗
Crimes against children are the most heinous crime. That, for me, would be a reason for capital punishment because children are innocent and need the guidance of an adult society. ↗
I don't think I would want the responsibility for enforcing the death penalties. There's always the inevitable question of whether someone you gave the order to execute might truly have been innocent. ↗