Really, though, when was the last time Oda gave every strawhat their only worthy opponent? Baroque works? I'm trying to recall some newer arcs... I don't think Nami and Usopp had a dedicated opponent in Skypeia, and Usopp and Robin didn't in Water 7. In Thriller Bark, there were only 4 main villains, and in Shaboandy it was the sumo kid and Kizaru.