Factual error: When we first see Kurgan in modern day New York, he begins to assemble his sword in a motel room. The very fact that he is assembling his sword the way he is, snapping segments together, especially the blade itself, which is segmented in the middle, would make that quite possibly one of the weakest and most inefficient weapons a person could ever wield. Being that it is segmented the way it is, it is structurally weak, and a clash against another sword, or any hard surface for that matter, would break the segments apart easily.
Factual error: The marine unloads his Uzi at Kurgen, about 10 seconds of full-auto fire. The Uzi fires at 600 rounds a minute, so can only fire for about 3 seconds (with a magazine the size he's using) before running out of ammo.
Factual error: When Connor and Kurgan fall through the roof at the end, they fall way too slowly than they would in real life. It takes them about 10 seconds to hit the floor in a building that looks about 30 metres tall.
Answer: What the punishment is isn't shown in this movie, but since even the Kurgan follows it, it must be high. In Highlander 3 we see that fighting on holy ground at least destroys the weapons they are fighting with (although only Macleod's for some reason), it's possible the ultimate penalty is given when an immortal kills another immortal on holy ground. A good guess is the penalty is death.
lionhead