#9-Shiliew of the Rain
Zoro has extraordinary mastery of Busoshoku Haki. He is also very skilled in the use of Kenbunshoku Haki.
#7–“Flower Sword” Vista
Vista is also capable of using Haki to fight Devil Fruit users. He is at the very least capable of using Busoshoku Haki, as seen when he fought against Akainu.
Jinbe is the most powerful fishman seen thus far. He is an exceptionally powerful master of Fishman Karate. He has a very high level of skill in Busoshoku Haki.
Benn Beckman is the first mate of the Red Hair Pirates. He possesses the highest IQ in East Blue and is probably strong enough to fight an admiral on his own.
Mihawk is the “Greatest Swordsman in the World”. Part of Mihawk’s reputation as the most powerful master swordsman in the world is also due to his tremendous superhuman physical power and fortitude which supplements his mastery of swordsmanship. He possesses an immense amount of skill in battle and has exceptional eyesight.
Mihawk is also shown to possess extraordinary mastery of Busoshoku Haki.
Silvers Rayleigh is the former first mate of the Roger Pirates. He has tremendous physical strength despite his elderly age. He is also a tremendously powerful and skilled swordsman.
Rayleigh is also shown to possess great mastery of all three types of Haki: Kenbunshoku Haki, Busoshoku Haki, and Haoshoku Haki.
#2-Monkey D. Garp
Garp is one of the most powerful Marines seen in the series so far and one of the major figures, along with Shiki and Whitebeard, from the times when the “Pirate King” was still alive.
His strenght is legendary, he is known for cornering and fighting Gol D. Roger many times.
He demonstrates extremely proficient skill in Busoshoku Haki.
He is known as the “Strongest Creature in the World”. Kaido has tremendous physical strength, as he once sunk nine enormous prison ships singlehandedly and defeated Eustass Kid, whose bounty is 470,000,000 Berries, with apparent ease. Maybe he has a devil fruit, maybe he doesn’t.
#Monkey D. Dragon
He is the World Government’s greatest enemy and is the most dangerous and most wanted man in the world. Dragon is already a powerful threat in his own right, as well as having powerful subordinates such as Sabo, Ivankov, Bartholomew Kuma, and Inazuma who are in comparison, lower in rank. This only speaks volumes of Dragon’s true power.
If it turns out that Monkey D. Dragon does not have a devil fruit, he is my bet for strongest non devil fruit user.
“Red Haired” Shanks takes the number one spot! He is Luffy’s role model and the man that our main protagonist wants to surpass one day. It makes sense in the series that Shanks is powerful because he is that character that the main protagonist wants to fight last on his journey. Shanks’ full fighting potential hasn’t been explored yet but there is a lot of hints that indicates Shanks is an extremely powerful individual. For starters, he was able to scare off a massive Sea King just by staring at it (until we figured out he used Conquerors Haki: the strongest form of Haki). He also clashed evenly with Whitebeard, a fellow Emperor and even fought another, Kaido, and arrived at Marineford without a scratch on him. Additionally, he managed to ward off Ankinu where the savage admiral seemed a bit shocked at his presence and stopped going after Luffy after he came. Most of all, Blackbeard, who had the powers of the destructive Gura Gura no Mi Fruit and the evil Yami Yami no Mi Fruit chose not to fight Shanks saying “he is not strong enough to fight him yet”. That right there makes Shanks a force to be reckoned with and definitely one of the strongest guys in the series.