The Warrior of Light is but a few hundred yalms away!
This (and its perfect inverse, the horrific solo instance in the Garlemald map of Endwalker) is one of the most affecting solo instances for me personally, because it does such a good job of instilling that feeling of needing to hold out to the very edge of hope.
The Warrior of Light is but a few hundred yalms away as you're fighting for your life, for your friends' lives, as you've been feeling the seconds tick by, waiting for reinforcements you are only certain are coming because of hope, is like... like looking to east at dawn on the fifth day in Lord of the Rings. It is the hope that you come to when you've run out of other hopes--that if you can only hold out long enough, you will not have to fight alone.
It just gets me so good every time.
What are some of your favorite solo instances?