You should really read Shamo, the main character is the defintion of a psychopath. Even if you don't like reading manga just read the first chapter and you'll be hooked... hell read the synopsis and you'll be hooked.
"At the age of sixteen Ryo Narushima was a genius and looked to have no trouble of getting into Tokyo University and joining the elite of society. However, that summer something cracked inside Ryo's head. With a small knife he brutally murdered both of his parents only leaving his sister alive and cowering in a corner. It is at this grotesque incident that our story begins..."
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http://myanimelist.net/manga/727/Shamo
"At the age of sixteen Ryo Narushima was a genius and looked to have no trouble of getting into Tokyo University and joining the elite of society. However, that summer something cracked inside Ryo's head. With a small knife he brutally murdered both of his parents only leaving his sister alive and cowering in a corner. It is at this grotesque incident that our story begins..."