If you don't speak Italian, I'd recommend renting from either Venice Rent or Europcar. The staff there doesn't speak English.

Service is good

For the second part of our trip, we rented a car. With the experience from the first part, everything went very smoothly. We rented the same model as before but found it too big, so we asked the rental company for a smaller one. Returning the car was very convenient; we drove to the parking lot, and the staff just checked the fuel gauge to complete the return. It was very quick.