Yes, darkest is a Scrabble word!

Adjective

1. Devoid of or deficient in light or brightness; shadowed or black

2. (used of color) having a dark hue

3. Brunet (used of hair or skin or eyes)

4. Stemming from evil characteristics or forces; wicked or dishonorable

5. Secret

6. Showing a brooding ill humor

7. Lacking enlightenment or knowledge or culture

8. Marked by difficulty of style or expression

9. Causing dejection

10. Having skin rich in melanin pigments

11. Not giving performances; closed