Death penalty is too good for them. A bit of fear and then peace.
I'd tie people like this up in a shit-infested windowless room alone. Each day cutting off a different body part bit by bit until they only have left what they need to be alive. Cut out their eyes, cut off their nose and cut out their tongue. Keep their ears just so they can hear the footsteps coming each day for a new torture. Keeping them alive by feeding them cat shit. And let them go crazy though solitary confinement before eventually letting them starve to death after years of hell