Thebans among others. There was apparently one instance when a Thessalian cavalry force bloodily routed an entire Spartan expeditionary force back to their ships with zero casualties (claimed, anyway) - presumably a surprise assault.

Quote Originally Posted by Cataphract_Of_The_City
But should you implement a type I goverment (spartan agoge) those Spartans would (or rather should) be as good as their ancestors.
I think you should read the relevant description in a bit greater depth. Anyway, back in the olden days the Spartans' chief advantage was always psychological - they were long the only true standing, professional army in the land of sunday soldier militias. Obviously that gave them a major edge in confidence in a straight clash (indeed the opposing phalanx often broke and ran even before contact, although this was by no means all that unusual in hoplite clashes), and a string of victories naturally grew them a fearsome reputation which only added to the intimidation effect.

But that was then. Several bloody routs sort of take the luster off such reputations.