You should remove "エって", because if even you the best kaido wanker says "Kaido the so-called strongest", it means you don't also believe that Kaido is the strongest unless .. you did that on purpose
It will not change anything, people continue to say that he is the strongest in the world, "say". They say it is.
it's up to you to believe, all over the world it is known as the WSC ... People say that WB is the strongest man in the world. Sengoku, Buggy, among others.
why would i delete this? People say that he is the strongest in the world, they are the basis of everything (you will not be known as the strongest in the world if you are not the strongest or if people do not say, this is how you become known) I have the fictional majority supporting me.
Kaido is said to be the strongest in the world. he did not suggest any other candidate to break his legitimacy, another character that makes people talk: some say that kaido is the strongest in the world, others say it is xxxx.
In another case in particular, it can be translated as:
or "the so-called strongest Kaido in the world". called = says ... in both cases, people say it is the STRONGEST.

Killer and Kid say that Kaido is the strongest pirate. In both cases, it is the people who say something, so it is the people who say that kaido is the strongest pirate.