17. Soviet Russia
This theory actually takes two interesting turns, one of which is far more plausible than the other, which is completely bonkers and sounds like something out of a thriller movie. The more plausible theory is nearly identical to the aforementioned Cuba theory. Nikita Khrushchev and Fidel Castro had allied against the U.S. by aiming an entire arsenal of missiles at the U.S. Gulf Coast during the infamous Cuban Missile Crisis of 1962, a crisis from which Kennedy obviously emerged the victor and greatly embarrassed the two communist leaders, meaning Khrushchev had just as much to gain over Kennedy being out of the way as Castro had. Critics of this theory argue that Oswald had previously defected to Soviet Russia where he met his wife, Marina and later returned to the U.S.. Upon Kennedy's assassination, this information would become public which would have made Soviet Russia the prime suspect had they enlisted Oswald to kill Kennedy. Then, there's the much more far-fetched theory that the Russians had enlisted a Soviet double to kill Kennedy and that Oswald had, in fact, never left Russia. Yeah, no.