Dear friend,
A mortal sin is an act that “destroys charity in the heart of man by a grave violation of God’s law; it turns man away from God, who is his ultimate end and his beatitude, by preferring an inferior good to him.” (#1855 Catechism of the Catholic Church)
So you are asking if preferring an inferior good to God can ever be good. This is like asking if darkness can ever give light. The only reason that God allows sin at all, is that a greater good can come as the result of a person’s repentance—but not directly from the sin itself.
Fr. Vincent Serpa, O.P.
