The quality of being unable to be appeased or placated.

अपरिवर्तनीयता

English Usage: His implacability was evident when he refused to forgive her.

Hindi Usage: जब उसने उसे क्षमा करने से इनकार किया, तो उसकी अपरिवर्तनीयता स्पष्ट थी।