Final answer:
The Aztecs and their native allies who fought against them with the Spanish both suffered from diseases like smallpox introduced by Europeans, as well as cultural and social upheaval following the Spanish conquest.
Step-by-step explanation:
The fate shared by the Aztecs and the natives who fought against them alongside the Spanish was largely one of tragedy and hardship. Both groups eventually suffered devastating losses due to diseases, such as smallpox, which the Europeans inadvertently introduced. While initially some indigenous groups, like the Tlaxcalans, allied with the Spanish against the Aztecs hoping for liberation, the fall of the Aztec Empire was met with cultural and socio-political upheaval that impacted all native societies in the region.
The Aztecs themselves faced the razing of Tenochtitlán and forced conversions to Christianity post-conquest. The indigenous allies such as the Tlaxcalans, despite their initial support for the Spanish, ultimately also came under Spanish rule and faced similar fates to the Aztecs in terms of subjugation and loss of autonomy.