Death is certainly not the worst thing that can happen to you. Redemption and acceptance of responsibility for one's actions are not mutually exclusive things. There is no reason I cannot seek (and even obtain redemption) - and still willingly accept the consequences of my behaviour. In fact, there is no reason I cannot accept even an unjust sentence. The 'executee' is free from concern over the justice of his/her fate (ie execution or no execution).

Capital punishment is an action taken by society-at-large. It is a public, dare I say, ritual in which finality is declared for gross transgressions. It should not be argued as a reasoned or corrective action for an individual behavior. The Christians with whom you argued apparently miss the point.

Capital punishment, as practiced currently in the US, is a extremely rare event (per capita) that serves as a symbolic, to those who support it (and the majority do). It is society's retribution.

Do I support it? Not particularly. Do I oppose it? No. Would I impose it? Maybe.