What culture produced the greatest warriors? I think it may be the Spartans, Romans, Samurai or knights Templar? Who do you think?

How do you define 'greatest'?

By number of people killed? Areas conquered? Honor system? Best training? What?

Well it depends on what you mean...

Samurai and Spartans were probably the most devoted and disciplined warriors. They fought often and devoted their whole lives.

European knights were the best equipped. They had the best weapons and armor (katanas dont even compare. They were sharp but short and homogeneous)

I think Spanish and Italian fencers/duelists were both the smartest and most skilled warriors. Spanish Destreza and Italian Fabris are both brilliant systems of fighting.

As a fencer, myself, I dont think it much matters.

I know people who could kill a man as easily with a spoon as they could with a sword. It depends on the warrior. If everyone's equal in skill, the winners are the best equipped. 16th century knights have the thickest armor and best weapons of the feudal era.

The mongols were the scourge of the known world at one point

Spartans, Romans and the Holy League, of which the Venetian Empire and the Spanish Empire were the main powers.