Put it near the end of an edit, after the moment of loss has already been shown, so the farewell lands as the closing beat. Follow it with Indian sad music to hold the mood, or lead into it from a quieter scene so the goodbye closes the story rather than interrupting it.
Über diesen Sound
This short clip is Tom Hanks as Chuck Noland speaking the Spanish line “Lo siento, Wilson” in a cracked, tearful voice after losing his volleyball companion at sea. It feels quiet, guilty and painfully sincere, turning a simple apology into a heavy farewell. It comes from the 2000 film Cast Away, where Wilson drifts away during Chuck’s escape from the deserted island.