Is it permissible, Islamically, to demand the return of a full financial grant along with a penalty, based on an employment contract whose agreed-upon duration was not completed due to unforeseen circumstances?

A fixed-term contract must be fulfilled because it is a binding contract. If the employee does not complete the term without a valid excuse, some scholars are of the view that he is not entitled to any compensation for the work he has done, similar to someone who was hired to carry a book but refused before delivering it, or to dig a piece of land but refused before completing the digging. Based on this, the company has the right to demand that you return the amount. As for the fine, it is a penalty clause.