This is “For the Need of the One” by Julia Ecklar. It’s Spock’s dying thoughts from TWOK.
It’s simple, short, and as moving now as it was all those years ago. In just a few words she references Spock’s behavior in STTMP, the Kobyashi Maru, and the deep emotion between Spock and Kirk.
It’s hard to pick a favorite line, but this one always brought tears to my eyes:
“There were none left but old friends and children
and I could not let their deaths weigh on me.”