No love for SWAT, Navy SEALs, or GSG9?
Most people seem to dislike/forget the modern warriors, though personally I found them to be some of the better episodes as well as having some of the best "simulations". (Who can forget the dancing Medellín Cartel member?)
I'd go with musketeer because they have a gun. Armour dosn't stand a chance against it if it hits and it would likely confuse people unfamiliar with the weapon. But the deadliest warrior thing is highly subjective, weather conditions, time of day, individual differences between people within the said periods, arbitrary luck of the moment, etc. Maybe one fumbles or makes a mistake. I suppose the Spartan stands a good chance if he brings along seven slaves with him, they were rather big slave holder and liked to bring a whole lot of them into the field with them.
I went with Mongol because they scared the shit out of Europeans for a while.
Yeah, the Mongol Empire got pretty big so I'm giving the nod to them. Some of these other dudes never challenged anyone outside their own country.
Musketeer since he has a gun, otherwise a late period knight would win
During the times of "Empire" it had multiple cases of enemy armes (without guns) loosing tens of thousands and the British army loosing less than two hundred.
Technology is the winner, always.
Apache for the sane fact that you want to die instead of being captured by them. Considering they put you either ontop of an ant hill/wrapped around a tree, they SLICE YOU OPEN and let either ants or wolves eat you alive as you watch... No... really, THEY DID THIS!