Is it obligatory to forgive the manager who incited hatred against me with his words, which forced me to leave my job?

Perhaps you were mistaken in accusing the manager, or the messenger was mistaken, so do not accuse the manager without clear proof. Even if you are certain of his misconduct, perhaps he had an excuse. Try to interpret his criticisms favorably and rectify your shortcomings. Forgiveness and pardon are paramount, for pardon is closer to piety, and patience and forgiveness are among the most resolute matters. Forgiveness increases a servant in honor. Therefore, we advise you to pardon and forgive, seeking Allah’s pleasure.