I was gonna say Sanji vs Queen, but Anime is making it very funny.
So I'll say Luffy vs Kaido, I think the Awakening was horrendous, every chapter ending Luffy/Kaido saying "Are you having fun" and the zero stakes or investment (or at least artificial investment) from the protagonists side.
Majority of OP fights are mediocre or not to be taken too seriously so there's lack of reason to hate on them.