Nazis are and/or were considered far right. Nazi stood for, in German, National Socialist Party, however one party rule. They allowed private ownership, except for Jews. They allowed capitalism, however it was crony capitalism. Communism is far left socialism with total government ownership of all property. Communist China has drifted away from pure Command Communism to a form of Nazism. One party rule but allowing capitalism to grow their economy. They can be far more dangerous, like Nazi Germany, than the Soviet Union was.
America is unique with 3 part government, executive, legislative, and judicial. It is supposed to be equal power to avoid a dictator. However we have developed huge bloated bureaucracys that are not elected. The large Federal government with it's bureaucracys has become a stranglehold on capitalism and private ownership and the persuit of happiness. The presidential position has obtained too much power through executive orders and appointments to head the bureaus. Congress has relinquished some of their power over the years.
Andrew Jackson was probably the first president to abuse his power, by disobeying a Supreme Court decision to NOT move the "Civilised" indian tribes to Oklahoma. Cherokees were the largest number. He said let the Supreme Court get an army and stop him. Of course most Americans liked this because it opened up a lot of land for settlement. It was not only Indian tribe in the south but also the midwest.
Abraham Lincoln also abused his power by suspending Habius Corpus during the Civil War.
FD Roosevelt got congress to give him the power of executive orders, which should have never happened.
Since then presidents have abused power by having "police" actions around the world without Declared Wars.
Now Obama is abusing power left and right. Ignoring a judgement to allow drilling back in the Gulf, giving amnesty to ILLEGALS recently. Using the EPA to get what he wants by shutting down coal power plants, suspending drilling permits on government lands, etc.