世界最強の剣士 = Sekai Saikyō no Kenshi = World's strongest swordsman
世界最強の男 = Sekai Saikyō no Otoko = World's strongest man
Here we have Mihawks and Whitebeards title. It should be clearly visible that both titles are very similar to each other, in fact the only thing they differ in is the last part. 剣士 means swordsman while 男 means man.
Both titles are build up in the same pattern: The first part is what they are, in this case the World's strongest, that is the same in both titles. The second part is the more important part as it states what group the first part refers to: In case of Whitebeards title it refers to the group of man, while it in Mihawks title refers to the group of swordsman.
Mihawks title is world's STRONGEST