The final saga of One piece officially began with the Egghead arc in 2022. The Straw Hat Pirates take center stage for most of the story, bringing with them youth and exuberance, as the manga is primarily aimed at the Shonen demographic. Despite this, even in the last section One piece story, some of the old characters remain incredibly relevant and their power still ranks them among the strongest in the world. With Haki of the highest order and powerful Devil Fruits to go along with it, One Piece's Final Saga is littered with old but powerful monsters, some of which even defy aging itself.

One Piece: All 9 Yonko Level Pirates in the Final Saga, Ranked
In One Piece's Final Saga, there are many powerful Yonko-level pirates all vying for power.
8
Silver Rayleigh
Silvers Rayleigh was once a member of the Roger Pirates that Luffy and the Straw Hat Pirates encountered on the Sabaody Archipelago. Rayleigh was known as the Dark King and was said to be on par with Gol D. Roger and Scopper Gaban. To be considered a rival to the Pirate King is quite a feat in itself.
On the Sabaody Archipelago, Rayleigh even demonstrated his power by taking on Admiral Kizaru using only his Haki. Rayleigh also reappeared on Amazon Lily and was able to intimidate the Blackbeard Pirates. In the God Valley flashback, Rayleigh was also seen to be strong enough to defeat a member of the Holy Knights with relative ease in order to save Shakky.
7
Scopper Gaban
Scopper Gaban is known as the Left Wing of Gol D. Roger, the late Pirate King. Scopper Gaban is currently around 70 years old. Since leaving the pirate Roger, he married and had a son in Elbaf. Despite his retirement on Elbafa, Gaban is still frighteningly strong and one of the greatest old men still alive in One Piece.
Gaban is canonically said to be a rival in power to Gol D. Roger and Silvers Rayleigh. According to Gaban, he was the second strongest of the Roger Pirates, behind the only captain. In Elbaf, Gaban was able to one-shot Sommers, one of the Holy Knights who has infinite regeneration. Without blackmail, Gaban could even defeat Gunk, Imu's close associate. Undoubtedly, his superior Conqueror's Haki control makes him a force to be reckoned with, even if he isn't the best.
6
Sengoku
Sengoku was formerly a marine admiral. Since the timeskip and his retirement, this position has been taken over by Akainu. Despite this, Sengoku remains an incredibly strong personality and one of the strongest old characters in the One Piece world. His previous position alone is a testament to his strength. A fleet admiral is even ahead of regular marine admirals.
His Devil Fruit, Hito Hito no Mi, Model: Daibutsu, was showcased during the Marineford Arc, and his shockwaves are terrifyingly overpowering, granting him god-like powers. He is also one of only two Marines strong enough to use Conqueror's Haki. Sengoku is still active in the final saga, but he may not be the most involved character.

One Piece: The Strongest Characters Alive After Elbaf
These One Piece characters will be the strongest after Elbaf.
5
Ragnir
In the current One Piece story, Ragnir is the hammer that ate the mythical Zoan Risu Risu no Mi, Model: Ratotaskr. This weapon is wielded by Loki, but has a mind of its own. As a weapon-eaten Zoan Devil Fruit, Ragnir has a will of his own and even remembers things he went through in his past lives from the One Piece Void Century. Ragnir is one of the oldest characters in One Piece in that sense, having met the likes of God of War, Imu, and even Joy Boy.
Ragnir is also incredibly strong. She and Loki make a scary pair, but even on her own she could put up a real fight for the likes of Loki, Harald and other legends. Defeating Ragnir was no easy task for Loki, which definitely shows how strong he is.
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4
Five elders
The Five Elders are the strongest force in the World Government, operating directly under Saint Imu Nero. The members of the Five Elders were formerly Saint Nusjuro, Saint Mercury, Saint Mars, Saint Ju Peter and Saint Saturn. However, at the end of Egghead, Saturn was replaced by Garling Figarland.
This group is incredibly overpowered and the sheer power they displayed during Egghead with their Yokai forms and their infinite regeneration makes them a force to be reckoned with. Even someone like Luffy tried to take them down. While their exact age is unknown, they are at least over 200 years old and potentially from the Void Century, except for Garling Figarland.
3
Zunesha
Zunesha is a huge elephant that is centuries old. Zunesha has been roaming One Piece for centuries, carrying the island of Zou on her back. Zunrsha's exact origins or her future role in the story remain a huge mystery, but her character has certainly captivated many.
Zunesha has known even the likes of Joy Boy, and even though he isn't exactly a fighter, Zunesha remains incredibly powerful just from her size and strength alone. With a single hit from the trunk, Zunesha was able to one-shot one of Kaido's All-Stars, Jack. He can definitely deal some lethal damage to most characters that cross his path, making him one of the most overpowered old characters in One Piece.
2
Monkey D. Garp
Monkey D. Garp is the grandfather of the protagonist Luffy. Garp is associated with the Marines, and while he is still present in the Final Saga, he is currently incapacitated due to being captured by the Blackbeard Pirates.
Garp put up a fantastic fight against the vast majority of Blackbeard's crew before being captured, and if Shiryu hadn't snuck him out, he could have single-handedly destroyed the Yonko crew, showing his strength even in his prime. Garp was also Roger's rival and had even performed the Conqueror's Haki of the highest in the present. A single blow from Garp could destroy an entire island.
1
Im
Imu is the secret ruler One piece world, sitting atop what was previously believed to be an empty throne in Marijoa. Imu has been a huge mystery since his introduction, but now, through the Elbaf arc, fans are getting a better idea of the character.
Imu's descent into Elbaf finally showed the true power of this individual and officially made him the strongest old character currently active in the final saga. Although Imu looks young, he is hundreds of years old. An imu that comes from the Void Century is definitely over 800 years old. Imu has the powers of a devil through his Akuma no Mi. He also has overpowered Haki, making him a fearsome demon strong enough to one-shot most characters, as seen when he easily defeated both Zoro and Sanji at once.