In January 2000, W.W.E. professional wrestler, Triple H, (Hunter Hearst Helmsley) had dubbed himself "The Cerebral Assassin", which implied that he was simply smarter than the other wrestlers.
Simply put into translation, it means, "Brain Killer", or someone who will knock you around, and do damage to your head. This specific title was used by professional wrestler Paul Michael Levesque's gimmick Triple H.
Someone who is so mind-nummingly retarded, they send you into a coma or vegatative state (i.e. those who are 13 years old, shop at Hot Topic, watch Twilight and Rick and Morty, and/or believe "real" Communism has never been tried).
Anon decided to be a CerebralAssassin today, and sent Chad into such a comatose state that he may never recover.