Which of the words CANNOT be formed by the letters of the word "NIGHTINGALE" using each letter only once?

Let's check the count of letters available in NIGHTINGALE:
$$\text{G:2, I:2, N:2, A:1, E:1, H:1, L:1, T:1}$$

* light: L, I, G, H, T are available.
* Thing: T, H, I, N, G are available.
* Angle: A, N, G, L, E are available.
* Eagle: Requires two 'E' letters (E, A, G, L, E). However, the word NIGHTINGALE contains only one letter 'E'. Therefore, "Eagle" cannot be formed.