If the Pope were to deny that the death penalty could be an exercise of retributive justice, he would be overthrowing the tradition of two millenia of Catholic thought, denying the teaching of several previous popes, and contradicting the teaching of Scripture.
The Church therefore has one inescapable task: To lift up Christ. When she seeks to lift herself up she becomes weak, but when she acknowledges her own weakness and proclaims her Lord, she is strong.