User blog comment:AztecJag/Aztec Jaguar Warrior vs Mapuche Warrior/@comment-37920093-20181225103053

Some interesting info:

According to an account by Bernal Díaz del Castillo, one of Hernán Cortés consquistadors, it could even decapitate a horse: Pedro de Morón was a very good horseman, and as he charged with three other horsemen into the ranks of the enemy the Indians seized hold of his lance and he was not able to drag it away, and others gave him cuts with their broadswords, and wounded him badly, and then they slashed at the mare, and cut her head off at the neck so that it hung by the skin, and she fell dead.

Another account by a companion of Cortés known as The Anonymous Conqueror tells a similar story of its effectiveness: They have swords of this kind — of wood made like a two-handed sword, but with the hilt not so long; about three fingers in breadth. The edges are grooved, and in the grooves they insert stone knives, that cut like a Toledoblade. I saw one day an Indian fighting with a mounted man, and the Indian gave the horse of his antagonist such a blow in the breast that he opened it to the entrails, and it fell dead on the spot. And the same day I saw another Indian give another horse a blow in the neck, that stretched it dead at his feet.

— "Offensive and Defensive Arms", page 23

Another account by Francisco de Aguilarreads: They used cudgels and swords and a great many bows and arrows, One Indian at a single stroke cut open the whole neck of Cristóbal de Olid’s horse, killing the horse. The Indian on the other side slashed at the second horseman and the blow cut through the horse’s pastern, whereupon this horse also fell dead. As soon as this sentry gave the alarm, they all ran out with their weapons to cut us off, following us with great fury, shooting arrows, spears and stones, and wounding us with their swords. Here many Spaniards fell, some dead and some wounded, and others without any injury who fainted away from fright.

Starts at 3:20 to 3:50.

The macuahuitl in the video wasn't of best quality, but still cut very deeply into the flesh and bone.