And if you don't know.

The Darkest Hour can be defined as when the villains of the story "win." Moreover, the reason as to why "win" is in parenthesis is because they don't win the whole story, but it's a very major victory.

Some examples are they manage to kill a major partner of the main hero's allies, there parents, or even turn everyday citizens against them.

So, can you name some. Oh and be sure to put down your spoiler tags for people who still haven't read that particular manga/anime.

I shall go first.

Yu Yu Hakusho
Sensui murders Yusuke in cold blood. He actually manages to kill the main character!

Black Cat
Creed kills Train Heartnet's girlfriend. That fiend!

Dragonball Z
Frieza does genocide on the Saiyans killing Bardock, Goku's father, and Vegeta's father as well.

Naraku has killed Kikyo so many times I lost count. He's a douche.

Death Note
That ba$tard Light Yagami kills L! Not only that but he has this menacing evil grin when he does it!

I wasn't prepared for it at all. Jiraiya gets impaled by Pein. X_X