Who is at fault if you are speeding into a parking space when the driver in the space to your right opens the door hits the front right fender of your car and nearly hitting the exiting driver?

It's debatable. There is probably some blame on both parties. There are laws regarding opening your door and/or leaving your door open in the flow of traffic. However, it would be easy to dispute that since a parking space would probably not be considered in the flow of traffic. It would probably depend on what each driver saw and what they did to avoid the accident. There is no definitive answer and no matter what anybody tells you, the accident is not clearly one person's fault.