Formally Hebrews 9:28 is indeed an exception: so Christ, having been offered once to bear the sins of many, will appear a second time (ek deuterou), not to deal with sin, but to save those who are eagerly waiting for him.
But the Lukan ascension, for instance, implies a similar pattern.
Otoh, the "first" time is "already" much of a multiple comeback, if you think of all the reminiscences of past characters that are explicitly or implicitly woven into the Gospel stories -- making the earthly Jesus appear as a second...Adam, Enoch (especially as the Son of Man), Melchizedek, Moses, Aaron, David, Solomon, Elijah, Elisha, Jonah, Jeremiah, even John the Baptist. Many of those historical, legendary or mythical characters being confusely expected to come (back or again) one way or another at the end of time. "He who comes" is made of many returns. At the center of the Synoptic Gospels, the narrative unit leading from the question "who do people say I am" to the Transfiguration story where Elijah and Moses merge into Jesus, so to say (Mrk 8:27--9), is exemplar in this regard.