Would you answer my question then. Does Buggy somehow killing WB make him the strongest in the verse?
Firstly, could you define what constitute a level above for you? From what I recall, you have the top tiers being extreme diff fights for each other, save Roger and Primebeard, who you think can high diff the rest of them. Mid diff is preposterous at the moment, nothing indicates Roger and WB were so above the rest. However, you I am sure already know that once Zoro beats his opponent, in most cases, the next time he fights them, he is able to beat them at a lower difficulty than before. Following the aforementioned pattern, once Zoro beats Mihawk extreme diff, theoretically the next time they fight, Zoro should be capable of high diffing Mihawk. Following that logic, that places him at a level you refer to as the PK level and that invalidates your statement. Moreover, the statement doesn't hold water, unless you think Mihawk is at the lower level of top tiers, and I sincerely hope you don't.
And why is the pirate king known as such? We actually got an answer to that recently.
As it's clearly visible in the panel above, Roger was crowned Pirate King because he was the first ever to complete a full circumnavigation of the globe. And how did Roger achieve that. Well, firstly he borrowed a crewmate from his biggest rival WB, in fact he was begging for it.
From Roger's own words he was certain that he could only reach the final island with Oden. Without having Oden, he as he himself implies wouldn't have been able to find the final island, and thus wouldn't have been crowned the PK. Furthermore, he was given two Road Poneglyphs by the Minks and Oden
Stole one from Linlin
No implication of a fight between them.
Got one from his friends the fishman
Exactly, Whitebeard could have been the PK whenever he wanted to, because Roger offered to tell him how to get there. However, would WB going there in any way make him stronger? No it wouldn't. What's more, we can infer that by the time Roger became the PK his health deteriorated more and more
which would logically make him weaker than he was, and would thus result in WB being stronger, even by a hair.
And why aren't the Yonko able to conquer the seas completely? Because there's 4 of them, 4 extremely powerful individuals interested in the same thing, becoming PK, besides maybe Shanks, who is in it to preserve balance. Kaido and Linlin each have a road poneglyph of their own. During Roger's time Kaido and Linlin were nothing like they are now
WB wasn't interested in it at all
and his other big rival was defeated via the effort of a mutual cooperation with Garp
That's how Roger became the PK.
