What are some Anime characters with dark sides.i also want to know the animes name

Lelouch Vi Britannia from Code Geass: Lelouch of the Rebellion. He has a sweet side, but when his dark side comes out it's ten times più awesome and exciting.

This guy is the darkest , he is the main character Tho

Zeref (Fairy Tail)

he is actually a poor guy who only luv peace but due to his dark magic an evil is inside him if it wake up he became a pure evil più like a destroyer of human race.............h ehe ehe h

The best one I know is Ukyo from Amnesia- his dark side is epic!

off the superiore, in alto of my head I can think of two

Yuno Gasai -Mirai Nikki
Yogi -Karneval

Nagisa (assassination classroom) This lil cinnamon bun, he's great. He's got the dark past the blood lust...ye. Good times. Luv this bae.

Ichigo Kurosaki from Bleach *-*