The macuahuitl was a favoured close fighting weapon of the Mexica warrior. To be sure they used other weapons too, but in surviving representations the macuahuitl predominates.
The macuahuitl was a flat hard wood baton up to four feet in length its edges were close set with razor sharp flakes of obsidian or flint or in coastal areas Sharks teeth. Clearly it was a cutting weapon. Some pictures of the macuahuitl show gaps in the sharp edges, it is conjectured that these maybe less lethal prisoner taking weapons. It occurs to me that they could just be cheaper weapons. A sumptuary analysis might confirm that and I may do one later.
To use a macuahuitl to best effect it would be necessary to strike your opponent hard and pull the weapon back or push it forward to bring the length of its edge into contact. Such an action would deepen and lengthen the initial wound. The resulting damage would be formidable and the blood loss considerable. I’d favour a backward return motion as this would leave the user well balanced for his next strike. A close reading of Conquistador testimony disproves the wide spread idea the weapon could decapitate a horse.
Just about every Conquistador who ever faced the macuahuitl was wounded, often repeatedly and their accounts of the Conquest make endless mention of wounds and treating the same. Few though were killed by one and we should consider why that was.
The Mexica and their native foes used quilted cotton armour. It may have been treated like the Greek Linothorax reconstructions to produce a light but resilient armour. None survives so we cannot know. It is though suggestive that the Spanish quickly adopted it as a supplement to or for poorer Spaniards a substitute for metal armour.
The Mexica military was meritocratic meaning the best warriors rose fastest in the army and society. Their military dominated their neighbours by virtue of skill and numbers. The Mexica were also by any standard very brave and were adaptive in tactics and weaponry.