Hubris, Thy Name Is Donald
Well, well, well. The mills of the gods grind slowly, but they grind exceeding fine.
Sin isn't a particularly active category in most contemporary New Pagan thought, but the ancestors, having more experience, and hence more wisdom, than we do—not to mention a worldview uncontaminated by knee-jerk reaction against natal monotheisms—accounted hubris as the chiefest of sins.
Hubris: excessive pride. (“Overweening” is the classic adjective here, but it's silly to define one unfamiliar term with another.) Not pride, note, but excessive pride: that's what the gods hate.
Well, gods, I'm with you on that one.
Of what does hubris consist? Of arrogating (whence “arrogance”) to oneself that which properly belongs to the gods. Thus, oddly, hubris is a form of theft: more specifically of sacrilege, stealing sacred property, accounted by the ancients as one of the most terrible of crimes.
For all the hallmarks of hubris, utterly lacking in the greatness of heart or nobility of spirit that characterize, say, Achilles, look to the former American Criminal-in-Chief: a life without honor, lived only for himself, in the misbelief that, for him, deeds have no consequence.