I don't know if I'm interpreting this the correct way but Oda is saying the lurking legend would be the greatest enemy for the Strawhats, has something to do with WB and is going to hinder to Strawhats in Onigashima. At first I thought Lurking legend and greatest enemy could be different characters but all these sentences seem to be linked with each other so it makes more sense that they are one and the same.
Kaido doesn't fit the lurking legend profile, nor did Oda not need to mention his name since everybody would have guessed that Kaido would be the greatest enemy in Onigashima? this is weird lol