Saying Shanks has another "power" doesn't really make much sense. He has no DF, he hasn't even a second arm anymore to use a gun (though it's not like a gun would add much value to a supposedly supreme grade blade wielded with proficiency). And yes, kicks won't add much value either. We know that you can infuse your blade with CoA and CoC. So whatever Shanks can do with his Haki alone, when channeled through his blade with his supreme skill, it is much better. That's why even Whitebeard, who has the strongest paramecia, uses a supreme grade blade. Because it makes him stronger. Let alone Shanks, who has no DF and great swordskill.
So who was the WSS then?
- Rayleigh
- Shiki
- Oden
- Xebec
No one was called WSS. So either there was an unknown character who magically was the strongest swordsman, or Oda simply didn't care to give this title to past characters from the old era, as only Mihawk is relevant to Zoro's goal.
