one man's decision could potentially destroy most of civilization.
I hope that isn't as true as Hollywood makes it out to be. Multiple authentication requirements, etc. are hopefully even stronger than they claimed they were _before_ Dr. Strangelove was released.
Turning back to antiquity, wasn't it Caesar who essentially tanked Rome? Though, "we" (civilization) will be taking the barbarians down hard with us if the nuclear option gets out of control.
No, Caesar changed Rome from a republic to an Empire. You could say he laid the ground works for the imperial Rome that we most often think of.
The fall of Western Rome was a drawn out process that took at least a couple of centuries, so you can't blame it on any one person. Rome probably fell for reasons not much different from why the Soviet union fell. It was too large an empire and way too reliant on central planning.