Newt was scared, absolutely terrified when Dumbledore told him it had to be him, that he had to be the one to stand against Grindlewald. The fear psychically gripped him for a few moments.
Newt Scamander had been scared a lot of things.
Of what his boggart would change into, of not being accepted, which didn't really matter to him now, of not being able to save the children he had failed to save, but never for himself.
This was a different fear.
With what happened to him in the subway with Grindlewald, Newt knew he didn't stand a chance against the dark wizard. How could he possibly?
As Leta was incinerated before his eyes, he felt nothing. Immediate denial and then acceptance. Then numbness. It was like his mind closed down.
All he could do was comfort his older brother. But Newt felt like he wasn't really there at all.
Theseus was weeping, he had lost the love of his life. And she had been his only friend. Who did she say "I love you" too? Perhaps the both of them?
While he barley shed a tear.
It scared him more than anything, than facing down the most powerful dark wizard.