Is it permissible not to deduct a dismissed employee's advance from his dues, given that he suffered clear injustice from the employer?

The injustice inflicted upon an employee does not justify concealing the loan due from him, because the accountant is entrusted with his work, and it is his duty to return trusts to their rightful owners. His work is a testimony, and he must be steadfast in justice, a witness for Allah, even if it is against himself. Likewise, he must offer advice to the oppressor to stop his injustice, and support the oppressed without betraying the trust, for example, by showing him the proper legal way to reclaim his right. It is not permissible for him to take money from the employer and give it to someone he believes to be wronged.