The more relevant part about the native american genocide as I recal is that it wasn't deliberate, or even purposeful- it was accidental and inadvertent thanks to disease.
While there are numerous recorded cases of sending smallpox blankets and such, those were after the initial wipeout. Something like, what, 99% of the north american indian population died to diseases from the first spanish expeditions centuries prior? Expeditions that in no way knew of or understood the diseases they were carying.
The vast majority of indians who died from smallpox never saw a European colonist, which is part of why Americans have the idea of the 'empty continent' myth of their founding. The US didn't have to conquer empires as it spread across the continent- the prior empires had already collapsed.
Small pox and the the settler diseases were simply that effective. They didn't need to be deliberatly spread to wipe out nearly all the local population.
Some genocide did occur. Take this account from a 16th century Spanish priest:
Yet into this sheepfold, into this land of meek outcasts there came some Spaniards who immediately behaved like ravening wild beasts, wolves, tigers, or lions that had been starved for many days. And Spaniards have behaved in no other way during that past forty years, down to the present time, for they are still acting like ravening beasts, killing, terrorizing, afflicting, torturing, and destroying the native peoples, doing all this with the strangest and most varied new methods of cruelty, never seen or heard of before, and to such a degree that this Island of Hispaniola once so populous (having a population that I estimated to be more than three million), has now a population of barely two hundred persons.
The island of Cuba is nearly as long as the distance between Valladolid and Rome; it is now almost completely depopulated. San Juan [Puerto Rico] and Jamaica are two of the largest, most productive and attractive islands; both are now deserted and devastated. On the northern side of Cuba and Hispaniola he the neighboring Lucayos comprising more than sixty islands including those called Gigantes, beside numerous other islands, some small some large. The least felicitous of them were more fertile and beautiful than the gardens of the King of Seville. They have the healthiest lands in the world, where lived more than five hundred thousand souls; they are now deserted, inhabited by not a single living creature. All the people were slain or died after being taken into captivity and brought to the Island of Hispaniola to be sold as slaves. When the Spaniards saw that some of these had escaped, they sent a ship to find them, and it voyaged for three years among the islands searching for those who had escaped being slaughtered , for a good Christian had helped them escape, taking pity on them and had won them over to Christ; of these there were eleven persons and these I saw.
More than thirty other islands in the vicinity of San Juan are for the most part and for the same reason depopulated, and the land laid waste. On these islands I estimate there are 2,100 leagues of land that have been ruined and depopulated, empty of people.
As for the vast mainland, which is ten times larger than all Spain, even including Aragon and Portugal, containing more land than the distance between Seville and Jerusalem, or more than two thousand leagues, we are sure that our Spaniards, with their cruel and abominable acts, have devastated the land and exterminated the rational people who fully inhabited it. We can estimate very surely and truthfully that in the forty years that have passed, with the infernal actions of the Christians, there have been unjustly slain more than twelve million men, women, and children. In truth, I believe without trying to deceive myself that the number of the slain is more like fifteen million.
The common ways mainly employed by the Spaniards who call themselves Christian and who have gone there to extirpate those pitiful nations and wipe them off the earth is by unjustly waging cruel and bloody wars. Then, when they have slain all those who fought for their lives or to escape the tortures they would have to endure, that is to say, when they have slain all the native rulers and young men (since the Spaniards usually spare only the women and children, who are subjected to the hardest and bitterest servitude ever suffered by man or beast), they enslave any survivors. With these infernal methods of tyranny they debase and weaken countless numbers of those pitiful Indian nations.
Their reason for killing and destroying such an infinite number of souls is that the Christians have an ultimate aim, which is to acquire gold, and to swell themselves with riches in a very brief time and thus rise to a high estate disproportionate to their merits. It should be kept in mind that their insatiable greed and ambition, the greatest ever seen in the world, is the cause of their villainies. And also, those lands are so rich and felicitous, the native peoples so meek and patient, so easy to subject, that our Spaniards have no more consideration for them than beasts. And I say this from my own knowledge of the acts I witnessed. But I should not say "than beasts" for, thanks be to God, they have treated beasts with some respect; I should say instead like excrement on the public squares. And thus they have deprived the Indians of their lives and souls, for the millions I mentioned have died without the Faith and without the benefit of the sacraments. This is a wellknown and proven fact which even the tyrant Governors, themselves killers, know and admit. And never have the Indians in all the Indies committed any act against the Spanish Christians, until those Christians have first and many times committed countless cruel aggressions against them or against neighboring nations. For in the beginning the Indians regarded the Spaniards as angels from Heaven. Only after the Spaniards had used violence against them, killing, robbing, torturing, did the Indians ever rise up against them....
---Bartolome de Las Casas, from A Brief Account of the Devastation of the Indies, 1542[\quote]