5. J. Edgar Hoover
Alright, let's face cold hard facts here: J. Edgar Hoover, who chaired the FBI when it was first established, was insane. In fact, he was mad enough that the FBI now restricts directors to a single ten-year term, and controversy over the J. Edgar Hoover building in Washington bearing his name is still very much alive today. Is he crazy enough to tacitly approve the assassination of a political enemy who just so happens to be the sitting commander in chief though? That's the subject for discussion here. There are those who believe that Hoover became aware of a credible threat to the President's life in the immediate aftermath of the Cuban Missile Crisis, but did not inform Secret Service about the threat and quietly swept it under the table. The theory here is that this threat regarded the attack in Dallas that ultimately claimed Jack Kennedy's life. Hoover was no friend of Kennedy's, as I said before, and allegedly wanted Kennedy out of the way so he wouldn't push mandatory retirement upon him in 1965 when he would be due to step down in such a situation. Bonkers? Yes absolutely, but I will say that considering Hoover's reputation for flagrant abuse of power, such an act would definitely be his modus operandi.