Although the anti-federalists lost their main goal, what important task did they accomplish?

The Anti-Federalists failed to grant the states the majority of the power (in a similar set-up to the Articles of Confederation), if I recall correctly. The important task they achieved was the addition of the Bill of Rights to the Constitution. They wanted to ensure that some of our most important rights were clearly defined and included in our nation's leading document.

Iwould say b but i’m not so sure

Idont get what your asking