In the early days of One Piece, seeing a new Devil Fruit User was an event. We can all get through major arcs in East Blue without coming across any Devil Fruit Users. Nowadays is different - Everyone has a Devil Fruit. When there is a top-class fighter and they don't have a Devil Fruit, that is now the event. In honor of the very strong without the help of magical fruits from the sea, Epicstream made this list.
There are characters who we do not yet know how strong or if they are Devil Fruit Users like Ben Beckman, Yasopp, or even Gol D. Roger. For that reason, they, and other unconfirmed users like them, will not be placed on this list.
SPOILERS AHEAD:
Nekomamushi & Inuarashi
Eiichiro Oda has taken many steps to emphasize that Nekomamushi & Inuarashi are equals on the battlefield. It is very easy to forget how strong they really are, but in their first appearance, they faced a monster like Jack the Drought for days and manage to hold their own. When Capone Bege got one look at Nekomamushi, Bege ran away.
Among the Nine Red Scabbards, Nekomamushi & Inuarashi are the two most powerful, and that is when they are still in their base form. Once the full moon is in full view in the sky, their enhanced Sulong form makes a Billion Beli pirate like Jack the Drought seems like an ant.
Vinsmoke Sanji
Arguably the weakest of the Monster Trio, he is still the strongest among them if we are talking underwater battles, as his Blue Walk can give him speed underwater equivalent to a Fish-Man. Due to his proficiency underwater, he has a niche fighting prowess, no Devil Fruit User can replicate.
Because of the Vinsmoke genetic modifications, he can now regenerate from huge injuries and is tougher than Armament Haki can allow. He is even fast enough that he no longer needs the Raid Suit to disappear. Due to his enhancements, he has now access in boosting all of his Black Leg Style abilities, and with practice will make Sanji even stronger.
At this point of the story, Sanji has just beaten Queen the Plague, one of the Beast Pirates' Three Calamities, and one of the toughest pirates anyone can ever face.
Roronoa Zoro
What is so impressive about Zoro is that he is at the level of Luffy's fighting abilities from day one, despite not having any evil Fruit abilities with just sheer hard work and determination.
Fast forward to now, he has honed his swordsmanship to the point that he is now one of the strongest swordsmen in the world, and while it might take a while until we get his legendary duel with Mihawk, with how Zoro is right now, there is no doubt that he can now at least last in the ring for a while with the world's strongest swordsman.
Not a lot of people can cut through mountains, but Zoro can. He just beat up Kaido's strongest crewmate while injured. At this point, there is no pirate crew in the sea that can face the Straw Hats.
Vista
We have yet to see much from Vista, and there is a possibility that we might never will. But from the little we have seen from Whitebeard's strongest swordsman, it is enough to put him on the list with confidence. If anyone can face an admiral and is not injured after the confrontation, he is in the big leagues.
Vista's biggest moment is when he faced Mihawk at Marineford. While they did not continue the fight to the end, Vista can still fight Mihawk on equal ground; he is the only swordsman on One Piece we have ever seen do that.
Sabo
While Sabo is known to be a Mera Mera No Mi User nowadays, this is still a fairly recent era of his life. A huge chunk of his career in the Revolutionary Army, Sabo did not have any Devil Fruit abilities. While we do not know if he can take on Admiral Fujitora without the Mera Mera No Mi, one cannot simply be the Chief of Staff of the Revolutionary Army without being one of the most dangerous fighters in One Piece.
Kozuki Oden
Kozuki Oden is not just a natural-born leader, but also one of the greatest swordsmen in the world. He is capable of facing both Whitebeard and Roger in a fight.
He is known most of all as the only person that left a scar on Kaido's invincible body, that is until Zoro made the same feat years later. It is left ambiguous if he can actually beat Kaido since Kaido's underlings interfered in their battle, leaving Oden distracted from Kaido's finishing attack. But the very reason we are asking that question speaks highly of Oden.
A strong man like Oden also deserves an epic death. Did he die being cooked in boiling water after an hour of lifting up 9 men so that they would not have the same fate as he? No. He died after being boiled alive in an hour, then being shot with a bullet. Like a boss, he smiled all the way to the grave.
Red-Haired Shanks
When Shanks was younger, he was a swordsman rival to the current strongest swordsman alive, Dracule Mihawk. We can stop there, but he also became a Yonko year later even despite not having his left arm. It is safe to say, if he never lost his arm, he could have been a Yonko with one arm tied behind his back.
Red-Haired Shanks's face is also seen when Kaido is remembering the few people that can fight with him on equal ground. Since Advanced Conquerors Haki is a prerequisite to harm Kaido in any meaningful way, then Shanks must have it.
Shanks is so powerful, he came to tell a war to stop, and the war being so scared, complied.
Dracule Mihawk
Dracule Mihawk is the first Shichibukai we have ever met, and what entrance did he make? He is the reason we put the Warlord position in such high regard.
If he has a title like The Worlds Greatest Swordsman, and can almost kill Zoro with the smallest sword in the world, we can only imagine what kind of monsters the other Warlords are.
The irony is, despite being the first Shichibukai in the series, we see and know next to nothing about him, but unlike the other Warlords who have that weakness, not knowing much about Hawkeye only adds to his mystique.
Everything about him speaks badass - His Musketeer-like design with sharp eyes, the way he casually roams the rough seas of the Grand Line with just a small ship and no crew. If anything, knowing more about him is the path to ruining his character.
Here's to hope that his inevitable duel with a certain three sword-waving individual will be all that's hyped up to be.
Silvers Rayleigh
As vice-captain of the Pirate King, and of the world's strongest pirate crew, Rayleigh is not only one of the strongest people without a Devil Fruit, but also one of the strongest in the world, period.
This guy can face an admiral in battle on equal ground and he is not even in his prime anymore. He faced Luffy in his Gear Fourth form, and he handled him like he is nothing.
His biggest feat of strength shown in the series is when he swam in the ocean hundreds of kilometers in the Calm Belt infested with Sea Kings so that he can reach Luffy on Amazon Lily. He even gets to see Rayleigh kill at least one Sea King on the way. That is one impressive feat, not even the strongest Devil Fruit User can ever do.
Monkey D. Garp
Garp does not have any Devil Fruit powers and just gets by with his awesome strength and mastery in Haki. Although, "getting by" may not be the word when we are talking about the most celebrated Marine officer of all time and Gol D. Roger's rival in their prime.
He could have been a Fleet Admiral by now if he really wanted to, he just doesn't want to. The biggest recent reveal in One Piece is the reveal that Garp once faced the strongest pirate crew in existence with the Gol D. Roger by his side. The Rocks Pirates included an all-star roster that included Big Mom, Whitebeard, Kaido, and so many more monsters. Garp and Roger won that battle.
There is no question Garp is strong. But is he the strongest?