Blackbeard as we know currently has two top tier devil fruits, you could even argue the best in their own categories.
I have no doubt that Blackbeard has Conquerors haki since he perfectly fits the criteria, but do you see Oda giving him the highest level of Haki alongside having two of the strongest devil fruits?
I have no doubt that Blackbeard has Conquerors haki since he perfectly fits the criteria, but do you see Oda giving him the highest level of Haki alongside having two of the strongest devil fruits?