I have Mihawk > Shanks but icl Black Blades at this point in the story don't mean anything so at this point for me I don't like to use it in a debate. Black blades clearly aren't only strength based. If they were why does Oden "nearly" make his blade black and how does Zoro who at that point was clearly weaker then Oden have a chance to make it black if he was way weaker. It doesn't make sense. Oda needs to lock in and explain Black Blades and why we as the reader should view it as special because at this point I don't believe it
He would have made it when he's stronger than Oden
He is already stronger than Oden but not Black Blade level