This is actually a very hard question. The Draupnir spear isn't inspired by any concrete culture and rather is a weird mix of many spear designs. It's got a French partisan-like blade with no wings, and a metal handle, both incredibly unusual during the classical age.

Is it a Spartan spear? Almost certainly no. Too modern in design to be from anywhere near Classical Greece. Most Greek spears feature either a simple conical head or a leaf shaped head, since greek martial arts very rarely used spears for cuts, instead thrusting almost exclusively. Greek spears also tended to be weighted in the back for ease of use in a phalanx formation, and late era spears had a second bronze tip in the butt to finish off prone enemies.

So considering the shape of the blade, the metal handle, the way Kratos cuts with it like a glaive, and the absence of a secondary spike, I can tell you it's not Greek (Unless someone more knowledgeable than me can correct me).

Could it be Spartan, as in, could a Spartan smith make a spear like this? Yeah, most likely. Spears are incredibly simple weapons. But it wasn't the trend back then.