The differences between the Federalists and the Antifederalists are vast and at times complex. Federalists’ beliefs could be better described as nationalist. The Federalists were instrumental in 1787 in shaping the new US Constitution, which strengthened the national government at the expense, according to the Antifederalists, of the states and the people. The Antifederalists opposed the ratification of the US Constitution, but they never organized efficiently across all thirteen states, and so had to fight the ratification at every state convention. Their great success was in forcing the first Congress under the new Constitution to establish a bill of rights to ensure the liberties that the Antifederalists felt the Constitution violated.
sources: The Gilderman institute of American history