Is it Islamically permissible to reclaim an apartment I gifted to my wife to soften her heart and avoid divorcing her, knowing that the initial intention was not achieved and our problems have increased?

A gift is not binding until it is seized. If the wife did not seize the apartment, and its ownership transfer was not officially documented for her, and the husband's control and disposal over it remained, he is permitted to revoke the gift. If the gifted apartment is their shared residence, her living with him is not considered seizure, except in exceptional cases related to a gift from one spouse to the other. The general rule is the prohibition of revoking a gift, except for a gift from a father to his child, or if the gift was given in exchange for something and that exchange did not occur, or if it was conditioned upon a purpose and that purpose was not achieved. If the apartment was gifted to the wife with the aim of softening her heart and this aim was not achieved, revocation of the gift is permissible. However, if the aim was achieved and then circumstances changed later, revocation is not permissible.