What is the ruling on naming a person "Abd al-Nasser" given that "al-Nasser" is not one of the Most Beautiful Names of Allah?

The names of Allah are definitive (Tawqifi), and there is no evidence that "Al-Nasir" (The Helper/Giver of Victory) is one of Allah's names. Therefore, it is not permissible to use "Abd al-Nasir" (Servant of the Helper/Giver of Victory) as a name for a person. This is an error from two perspectives: naming Allah with something that has not been revealed through divine scripture (Al-Sam') and worshipping by a name that Allah has not named Himself with. If it is possible to change the name in official documents, then do so. Otherwise, change your name in your interactions to another name, such as "Abdullah" (Servant of Allah), and there is no blame on you for the name in the documents if you are unable to change it.