What difficulties did Shang Jun encounter in the process of political reform? Because of which measure in the reform?

Shang Jun's political reform was tortuous, and the biggest difficulty came from the strong opposition and confrontation of the conservative nobles of Qin State to Shang Yang's political reform. Because the prince broke the new law, Shang Yang did not hesitate to severely punish the two teachers of the prince and established trust in the people, so that the new law could be implemented in Qin State. In the reform, the biggest blow to the old aristocratic forces was to abolish the old system of recording records in the Qing Dynasty and implement the military service system. Nobles are no longer eternal nobles, and civilians can also improve their social status through meritorious service.