darkest

adjective

• Having an absolute or (more often) relative lack of light.

  "The room was too dark for reading."

• (of colour) Dull or deeper in hue; not bright or light.

  "my sister's hair is darker than mine;  her skin grew dark with a suntan"

• Hidden, secret, obscure.
• Without moral or spiritual light; sinister, malign.

  "a dark villain;  a dark deed"

• Conducive to hopelessness; depressing or bleak.

  "the Great Depression was a dark time;  the film was a dark psychological thriller"

• Lacking progress in science or the arts; said of a time period.
• With emphasis placed on the unpleasant aspects of life; said of a work of fiction, a work of nonfiction presented in narrative form or a portion of either.

  "The ending of this book is rather dark."