The most controversial provision in the 42nd Constitution Amendment is the primacy given to the Directive Principles over the Fundamental Rights.

The 42nd Constitution Amendment Act was enacted in 1976 during the period of emergency in India. It brought about several significant changes to the Indian Constitution, and one of the most controversial provisions was the primacy given to the Directive Principles of State Policy (DPSPs) over the Fundamental Rights.

Directive Principles of State Policy (DPSPs):
1. The DPSPs are a set of guidelines and principles given in Part IV of the Indian Constitution. They provide directions to the government in policy-making and aim to establish social, economic, and political justice in the country.
2. These principles are not enforceable by any court, and their implementation is left to the discretion of the government.

Fundamental Rights:
1. Fundamental Rights are a set of basic rights guaranteed to all citizens of India. They are enshrined in Part III of the Indian Constitution and are justiciable, meaning they can be enforced by individuals through the courts.
2. These rights include the right to equality, right to freedom, right against exploitation, right to freedom of religion, cultural and educational rights, and the right to constitutional remedies.

Controversy:
The controversy arises from the fact that the 42nd Amendment Act gave precedence to the DPSPs over the Fundamental Rights. This means that if there is a conflict between a law enacted to implement a Directive Principle and a Fundamental Right, the law will prevail over the right.

This provision was seen as a dilution of the importance of Fundamental Rights and a shift towards a more socialistic ideology. Critics argued that it gave the government excessive power to curtail individual rights in the name of implementing social and economic policies.

Impact:
1. The provision led to a number of legal challenges and debates regarding the balance between individual rights and societal welfare.
2. However, subsequent amendments and judicial interpretations have clarified that while the DPSPs are important, they cannot be used to override or violate the Fundamental Rights.
3. The 44th Constitution Amendment Act, passed in 1978, restored some balance by deleting the controversial provision and reaffirming the supremacy of Fundamental Rights.

Conclusion:
The controversy surrounding the primacy of Directive Principles over Fundamental Rights in the 42nd Constitution Amendment Act highlighted the delicate balance between individual rights and the welfare of society. While the amendment sparked debates and legal challenges, subsequent amendments and judicial interpretations have ensured that Fundamental Rights remain paramount in the Indian constitutional framework.