#8 "The Charismatic Enigma" Jeff Hardy
If you're closely analyzing what Jeff Hardy has been doing recently, then you do understand that he has certainly walked a dark path inside his head.
Jeff Hardy's characters have successfully complimented his in-ring style, and have been influential in ascending the quality of his feuds.
Whether it was his feud with CM Punk, or his recent altercation with Randy Orton, Jeff Hardy has always had that dark edge to his character that only exposes when he is at his best.
His Extreme Rules match with the Undertaker on an episode of SmackDown in 2010 also depicted how fearless he becomes when he starts coercing his mind to the dark side of life.
Considering that he's bound to be Brother Nero soon, the Charismatic Enigma is leaving no stone unturned by constantly explaining the chaos that transpires within his mind.
He appears broken and applies face paint to transform into a fractured identity. Whether you're a fan of Broken gimmick or not, Jeff Hardy has certainly walked a dark path in his career, and that is why he's probably one of the darkest characters in WWE.