"Native American" covers a lot of ground, both literally and metaphorically, spanning numerous cultures occupying a wide array of environments and at varying degrees of cultural complexity. Do you refer to the complex and well-developed cultures of middle America, like the Aztecs, who had a well known thing for human sacrifice? - Quite necessary for the propagation and well being of the universe, according to what we understand of their cosmology.

I am sure you can cherry pick the writings of any group and enter them in a "most spiritual" contest. Christians have said a lot of very spiritual things, and then there is the Inquisition....