I wouldn’t limit it to just the Aztecs.
Early archeologists thought the Mayans were all sweetness and light, but not too many years ago, they discovered a basement mural of theirs that was grotesque beyond belief. It depicted how they conquered another people and spent six months horribly murdering them. All of them.
Their ancient city at Tikal, Guatemala is a four and a half hour walking tour. With very tall pyramids and artificial lakes. Everyone assumed it was their capital, until 20 years ago, when a geologist found a mountain ridge line north of there was instead a buried city maybe four times as large.
They’re not even sure who built the great pyramids at Teotihuacan, north of Mexico City, but before they accidentally removed the top half of the larger one, thinking it was rubble, it was larger than the pyramids at Giza. Estimated population of the city around 500 AD was 125,000 or more, one of the top 10 in the world at that time.
And the Conquistadors didn’t even arrive for a thousand years after that.
And South America had giant empires we had no idea existed until we found traces of them via satellite.
The amount of savagery is beyond estimation.
Thanks y.
http://www.bigtravelweb.com/travel/2012/03/22/remote-maya-ruins-of-central-america/
https://www.google.com/search?q=remote%20sensing%20precolumbian%20sites