I've probably spent most of my life feeling that there are some crimes by some people that are so heinous the best solution is removal of them.
But there have been too many cases of mistakes or deliberate corruption of the system. If we sentence someone to life and we are wrong we can correct it. The death penalty (other than that one supposed crucifixion) doesn't allow for correction.
Our whole western justice system is designed with a bias to not convicting the innocent. This results in the guilty going free sometimes but that's the bias we have chosen and I'm in agreement with that.
With capital punishment I agree it is better to keep the evil alive than ever kill the wrong person rarely or not.