The Arafat incident is one case. His disrespect for the 2nd Amendment is well documented. He made NYC a "sanctuary city", flaunting federal immigration laws. He tried to illegally extend his second term, citing 9/11 as an emergency.
Each of those, perhaps, could be reasoned away. But as a whole, I see a very dangerous pattern of absolutist authoritarianism that would be extremely unwise to be allowed in a U.S. President.
Don't forget his hauling his official mayor records away to a warehouse, in violation of the law.