The Spanish Catholics were somewhat better in that after they beat their religion into the natives, they let them live as slaves. The ones who didn't convert were killed of course. But the "American conquerors" were worse.
One of my ancestors who was an old man at the time was killed by fundy-type christians by having a burning tree branch shoved up his bum.
the worst war crimes ive heard of are the europeans when they first came to america and slowly tortured all the natives by doing things like slowly burning them alive over weeks. they used their religion as an excuse and said they were doing gods work burning the sin out of heathens. I imagine the new americans were just as horrific to the remaining native americans many years later