Firm or unable to be changed or influenced.

अडिग या अपरिवर्तनीय

English Usage: Her confidence in her decision was unshakeable, no matter the criticism she received.

Hindi Usage: उसके निर्णय में आत्मविश्वास अडिग था, चाहे उसे कितनी भी आलोचना क्यों न सहनी पड़ी।