With the conclusion of Whole Cake Island earlier this year and the manga entering Wano – there has been many doubts on how are we going to defeat the Yonkos.
Big Mom tanked a G4 Kong Gun which didn’t even left a scratch, while Kaido is shown to be unkillable. We know Shanks is a total badass, but we are far from knowing his true capabilities, but it’s no doubt that he’ll be as strong as BM and Kaidou. I’ll get to Teach later.
With the Anime starting phase 2 of the Luffy vs Katakuri fight, viewers were thought that there is another level of Observation Haki and Armament Haki. Observation requires full concentration and composure (basically, cool calm and collected) to unlock the next phase, which is either future sight, or a different way depending on the user. There is not much detail on the next phase of Armament, but it’s safe to say G4 is of similar level – so it is safe to assume that raw strength is involved as well as determination.
However, one thing not mentioned is Conqueror’s Haki. We all know the extent of Conqueror’s Haki, especially when two users unleash it, but that is all we know.
In my opinion, the strength of the Yonkos (applying Big Mom, Kaido and Shanks) is due to their understanding and master in the arts of Conqueror’s Haki. There should be 2 sides of Conqueror’s Haki aside from affecting the surroundings and others, which affects one’s self – Defensively and Offensively.
Big Mom has both – enabling her to have an innate indestructible exterior defensively, while offensively enables her to have a broad reach in her Conqueror’s Haki, however, due to her unstable mind, these 2 aspects turn to pure strength when stress induced.
Kaido, on the other hand, is a master of Defensive Conqueror’s Haki, hence he is literally unkillable because even the forces of nature bend to his will. Of course, aside from pure strength and the monster that he is, this makes him basically immortal – and he can’t even stop it himself as he was born to conquer. Basically, imagine his body emitting an aura that stops anything from killing him. While his mind wants to suicide, his body will not.
Shanks on the other hand is a master of Offensive Conqueror’s Haki. No doubt he will have mastered Conqueror’s Haki and Armament Haki, but what makes him a Yonko is how he utilizes his Conqueror’s Haki offensively to intimidate his opponents, despite his small stature compared to the other big dogs in the New World.
Basically, as there is another level to Observation Haki and Armament Haki, there is also another level for Conqueror’s Haki. The Yonkos are strong because they have fully learned how to master it – and this is how Luffy will gain his next powerup.
Teach on the other hand, is due to how he has fully mastered his Devil Fruit – and is totally reliant on it. Couple that with the fact that he has 2 devil fruits, even with Haki, Teach is able to counteract anyone with the Yami Yami no Mi, and cause destruction with the Gura Gura no Mi.
Not to say he does not have strong Conqueror’s Haki (or Observation Haki/Armament Haki for that matter), but Teach is innately strong to begin with, and is backed up by 2 strong devil fruits.
*Theory by ELDIABLIU