Yeah, I'm nuts because the only guy with a black blade in the world who duelled with Shanks = Vista. Dude, shut up.
You welcome xD
Now if being serious, let's justy talk about things:
1. We know that Roger was strong as WB in prime, who was known as Strongest man in the World, after Roger's death. Now, Roger was a swordman, so you could easily call him strongest swordman in the world. Shanks was just like cabin boy, and was never even close to his captain and his commanders;
2. Shanks fought Mihawk and was equal to him, before he lose his arm, and that time Shanks was not even close to WB and Roger;
3. Mihawk never fought WB(he faced him in MF first time in his life), Kaido or supposely BigMom;
4. Mihawk never fought against Vista, who was best swordman in WB crew;
Now tell me, WHO was the ONE that Mihawk defeated and became WSS? WHo was the one, who defeated Roger? I don't know anyone like that, and because of that and many things that happened with Mihawk in Marrinford(Vista/Crocko/Mr1 clash, wasn't able to kill luffy), I call his title as FAKE, and feel fishy thing about him.