What is the Sharʿī ruling regarding a medical student who performed an abortion on a girl, knowing that he is now in the final stage of his training, and should he refuse to perform it again if asked, given that his objection might affect his graduation?

Your friend committed a haram act by aborting, and he must initiate repentance. Abortion is forbidden at all stages of pregnancy except for a valid legitimate reason, such as the mother's life being in danger based on a report from a trusted doctor, or the confirmed death of the fetus. Fear of not graduating is not an excuse, and the fact that abortion is permissible under Chinese law does not justify his action, and he must clarify that his religion does not permit it.