Which leader was against the formation of political partys?

George Washington

Explanation:

George Washington was generally skeptical of the role of political parties in a democracy. He believed that having different parties could potentially lead to sectionalism, which could threaten the unity of the nation. He also believed that the conflict that arises between different parties weakens the government, as they try to take the power for themselves and forget about the good of the nation as a whole.

George Washington. He had spoken out against them during his farewell address.