And so, Zoro returned to the Straw Hats, after 2 years of training.
We've yet to see him getting serious against an enemy. So far, he's seen his fights as some sort of warm-up or simply as a joke.
We just need to see his fight against Hyouzou, the strongest swordsman on Fishman Island, and who also had a boost in strenght thanks to the Energy Steroids. In this fight, Zoro gave one of the most epic and badass quotes in the series, so far, "You wanted to kill me? You couldn't even kill my boredom.."
He truly is the most badass member of the Straw Hats ...yes, even when he's lost... haha