Who is at fault if you were driving in a private lot and someone parking spot backed into thought stopped but the person who was hit said reverse?

It is difficult to say who is at fault without knowing the specific facts of the case. However, generally speaking, if you were driving in a private lot and someone parking spot backed into you, although you stopped, the person who was hit said reverse, the other driver may be liable for the accident. This is because the other driver had a duty to yield to you, as you were already in motion. Additionally, the other driver may be liable if they were backing out of a parking space without looking or if they failed to use their turn signal.