I don't have the mind of a psychopath, but I'd rather take out an FA than my captain. Would require much less effort. But again, even with two strong dudes up there, a third guy can do some serious damage. (Again, see
FedEx 705)
But more importantly, on a Boeing aircraft, you might not even need to harm the FA. Just disconnect the autopilot, full throttle, pin the yoke, and in time the aircraft is breaking up at nearly supersonic speed and the FA has long been pinned to the windshield due to G forces. (See
SilkAir 185)