I would guess that them most unDemocratic aspect of the US Constitution is the creation of the US Senate. Perhaps the most unDemocratic aspect of any Democracy. The states of Wyoming, Vermont, Montonna, North Dakota, South Dakota and Alaska which together contain 5 million people have the same power in the Senate as do New York, California, Texas, Florida, Ohio and Illinois which have 140 million people. A factor of 28 times as many people.