Spartans were stronger in numbers, and when going up against an armoured opponent that is also marcially trained they could be at a disadvantage.
Also, a knight's armour is mostly the result of arms races with the weapons present in their time, weapons that are superior to those of the Spartans. A Spartan probably couldn't do so much against their armour.
Spartans were good though, and do have a chance at winning, but they would have to work much harder to kill the armoured knight than the knight would have to to kill the Spartan.
A spartan because of his shild and he starts training when he is one
A spartan
Spartan In a fair fight, yes Spartan would win, but Ninjas don't fight fair.
The knight is the clear winner, due to the thousand year technological advancement. The Spartans aren't as great of warriors as media portrays them. Spartans rarely wore bronze (only the richest Spartans wore it) and preferred Linothorax, a cheaper mesh of leather that is almost as strong as metal. The knight, however has full body steel armor on top of chain mail, than a thin sheet of leather. The Spartan's weapons would snap in half before they penetrated that armor. While the Spartan's training is better, he was trained to fight the leather armored and wooden shielded Persian, not the Steal coated Knight. The Sprtan would have a very hard time trying to break through the steel, and would eventually time himself out, and all the knight would have to do is stand there until the spartan gets tired than he finishes the fight.
Spartan, due to superior weaponry, armor, training, and physical fitness.
space marine
Batman always prevails in the end.
They don't fight monsters they fight dragons. Calling for God's help.
Kratos.
sonic
They were obedient to their leader and were taught to fight until they died.
A typical day for a knight was serving his lord which gave him land money and protection if the knight would fight for him against other lords