“We get Grey Worm’s stoic determination breaking down as his eyes grow wider” - Not at all how I saw it. To me he realized that he now has something to live for, and had to make a choice between certain death in honor of duty, and making the harder choice to fight for survival.

This is how Ayra did it. Right as the Night King is looming above Bran, there is brief cutaway to the face of one of his lieutenants. You can see an eye blink, something no White Walker would ever do. Ayra has killed it and using her faceless man skills, was hiding in plain sight. Even then she couldn’t catch the…