The most significant achievement of the United Nations Organisation (UNO) since its formation is the

The most significant achievement of the United Nations Organization (UNO) since its formation is the prevention of another world war. The UNO was established in 1945 after the Second World War to promote international peace and security, and one of its primary goals was to prevent another global conflict. The UNO has been successful in this mission, as there has not been a third world war since its inception. The UNO has played a critical role in resolving conflicts, promoting disarmament, and fostering cooperation among nations, which have helped to maintain peace and stability in the world. Although there have been regional conflicts and tensions, the UNO has been instrumental in preventing them from escalating into a global conflict.