L.
Kaido's title has never been put in an introduction box.
Oda has never refered to it without "known as" "said to be".
Unlike WB or Mihawk.
Also World's strongest PIRATE isn't WB's title, his title is World's strongest MAN, but he's so strong that he is ALSO called World's strongest PIRATE by ODA and NARRATOR alongside that.
Kaido is only WSC because people believe he CANNOT DIE, it has NOTHING to do with his actual achievements or strength.
WB proved the world he was WSP through his LIFE achievements
Kaido was called WSC because he is seemingly IMMORTAL.
WB>Kaido bru