I mean… except for when they were separated, it was always Straw Hats job to defeat the antagonist. But in this arc, they've beaten only two out of all them, going up to three when we count upcoming defeat of Doflamingo.
Actually 5 (Jora, Sugar, Senor Pink, Pica and the eventual Doula Mongo), 7 if you count Buffalo and Baby 5 at PH. And then there's Monet.