The Anti-federalists were able to get a Bill of Rights added to the new US Constitution.
Initially, the Anti-federalists wanted to merely amend the Articles of Confederation at the Constitutional Convention. However, this task seemed nearly impossible considering how many votes were needed to make amendments to the Articles of Confederation.
Instead, the Constitutional Convention proceeded by developing a brand new constitution. The federalists did not want to add a bill of rights, as they felt it would be dangerous and would actually limit the rights of citizens. On the other hand, Anti-federalists felt that it was imperative that there was a concrete list of rights that citizens had that could never be taken away by the government.
In the end, the federalists got the new constitution they desired while the anti-federalists got the list of guaranteed rights they desired.