The top of the mountain is a lonely existence in One Piece, since very few can challenge the Pirate King themselves.
As the saying goes, "Might always makes right," whether it's a work of fiction or the real world. Some of the strongest One Piece characters redefine the concept of power. Gol D. Roger is highly regarded as one of the most dangerous in the series. However, there are a select few who can definitely fight on equal footing.
This article is based off of currently known feats. One Piece characters like Dragon and Im are excluded from the list, since nothing is really known about them. Rocks D. Xebec is an exception to this rule, since the story directly states his threat level. Anyway, here's a look at the most fearsome monsters in One Piece.
Five of the strongest known characters in the One Piece series
One Piece readers already know that Kaido's reputation is fully-earned. This is a monster who can strike fear into the heart of Donquixote Doflamingo, a man who is more than willing to provoke the World Government. Even characters like Luffy can go down in a single hit.
Kaido has the highest-known bounty of any pirate alive today, with over 4,611,100,000 belly. He's only lost seven battles in his entire career, which says a lot. The Onigashima Raid is a prime example of just how much damage he can do, even against multiple opponents.
His Devil Fruit is classified as a mythical Zoan type, which is exceedingly rare. Kaido uses it to his full advantage, ant it gives him plenty of offensive and defensive abilities.
2) Edward Newgate aka Whitebeard
Back in his prime, Whitebeard could directly swing blades with the Pirate King himself. Whitebeard's use of the Gura Gura no Mi was so powerful, he had the potential to destroy the entire world. He was not a man to mess with in One Piece, which still proved true in his old age.
Although he was in a state of near-death, Whitebeard was still considered the Strongest Man in the World. When he went to rescue Ace, the Marines had to use everything they had to stop him. A fully-enraged Whitebeard is extremely dangerous, as Akainu found out the hard way.
Even when he finally went down to Blackbeard and his crew, Whitebeard took an insane amount of damage. He was already a very old man by that point, yet he delivered as much damage as he received. The Marineford arc would've played out much differently if Whitebeard had been younger.
3) Monkey D. Garp
Roger didn't consider many people to be worth his time. Garp is one of those few exceptions, which is a testament to his skill and strength. Not only did he take on the Pirate King several times, Garp also rivaled him in power.
Garp has repeatedly turned down offers to become an Admiral, which puts him on a similar footing to Akainu. His family lineage is also considerably strong, with a bloodline that includes Dragon and Luffy.
He was even able to knock down Marco rather easily in Marineford. Keep in mind that Marco can handle the likes of King and Queen at the same time, and their bounties exceed billions. Even in his old age, Garp is one of the more powerful characters in One Piece.
4) Gol D. Roger
The Pirate King needs no further introduction, given his mythical status as a great fighter. Roger possesses the highest-known bounty in the series, worth over 5,564,800,000 belly. To put his strength into perspective, Kaido and Big Mom still haven't broken that record despite outliving him.
Roger is among the rare few who can directly engage in combat with the likes of Whitebeard. This is someone who fully mastered his Haki, to the point that he can use advanced techniques nobody else can. Roger also wields a Supreme Grade Meito, the likes of which are known for their excellent craftsmanship.
Despite his death, he is directly responsible for ushering in a new age of piracy. One Piece wouldn't exist without Roger's famous declaration. His charismatic personality is another aspect of his true power.
5) Rocks D. Xebec
It's true that not much is known about Rocks, who came to power over 40 years ago. One Piece Chapter 957 revealed just how terrifying he truly was. It took a combined effort from Roger and Garp just to bring him down. There is a reason why Rocks is considered Roger's most dangerous adversary.
Keep in mind that most of his crew went on to become powerful Emperors, such as Big Mom and Kaido. For a man who wanted to become the King of the World, this speaks volumes about his legendary reputation.
Even someone like Kaido holds Rocks in high regard. Back in One Piece Chapter 1001, Kaido described his former captain as a true equal.
Note: This article reflects the writer's personal views and is not in any particular order of ranking.