The Last Adam is the designation given to Jesus by Paul in 1 Cor. 15:45, "The first man, Adam, became a living soul. The last Adam became a life-giving spirit." As the first Adam represented those 'in him", the Last Adam, Jesus, represented those "in him" as well. 1 Cor. 15:22, "For as in Adam all die, so also in Christ all shall be made alive."
Adam was a type of Christ. Rom. 5:14, "Nevertheless death reigned from Adam until Moses, even over those who had not sinned in the likeness of the offense of Adam, who is a type of Him who was to come."