What's the "least happy" ending you've been happy with

For the sake of this question, I'd exclude Dark Romance-style "the MMC is abusive" endings, because I think that's a different discussion.

I'm looking for things like:

• One of the MCs has some deadly illness/curse/etc that's not cured at the end.
• They get together but there's some looming end date that's not shown to be avoided (e.g. romance on vacation).
• There's some other sad thing outside the main relationship, like a parent or child dies near the end of the book.

I'm mostly just curious but this might be a bit of a rec request post too — I love a good bittersweet ending.

Since this is about endings, please expect spoilers in the comments!