1. His jihad against the free press, to the point of suggesting the possibility of "opening up" unconstitutional libel laws and his banning of certain members of the press who write things about him he doesn't like.

2. His cavalier threat to imprison political opponents.

3. His threat to impose martial law in order to solve crime and his pledge to bring back torture in violation of the Geneva conventions.

4. His scapegoating of unpopular minorities for political gain (Muslims, Mexicans, etc)

5. His complete lack of transparency, especially regarding his finances, which his supporters let him get away with.

6. This threat, as an actual agenda item, to deport American citizens.

7.  His threat to engage in unilateral warfare to retaliate against international trespasses like obscene finger gestures.

I could go on but I only have so many characters to play with. The signs of creeping authoritarianism are all over the place for those with eyes to see. Only the willfully blind cannot.