Christian: The bodily return of Jesus on the last day to judge the world.
ACIM: The collective return of our awareness of the Christ, our true Identity. A time in which all minds are freed of the ego’s rule. The First Coming of Christ was God’s creation of our true Self; the Second Coming is the return of our awareness of our true Self. It ends the Holy Spirit’s lessons and allows all minds to hear the Holy Spirit’s judgment, which is the basis for what comes after it: the Last Judgment (see W-pII.10.1:1-2). Though it is not the return of Jesus, he is in charge of it. See T-4.IV.10, T-9.IV.9, W-pII.9.