The Marines are one of the major powers in One Piece. They ensure that the number of pirates doesn't get out of control. They are the "good guys." Koby holds the position of Navy Captain. He got to the position with his incredible hard work.

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Ever since he was a kid, Koby wanted to join the Marines. But due to an unfortunate accident to become a part of Alvida's crew, Luffy turned out to be his savior. Koby trained under Garp and the training enabled him to rise through the ranks. Koby has got a long way to go before he can become a Navy Admiral.

10 CAN'T BEAT: Fujitora

Fujitora using a transponder snail during the Dressrosa arc in One Piece

Fujitora joined the Marines after Aokiji and Akainu finished their fight. With Aokiji leaving and Akainu being promoted, there were two spots open. He joined the Navy via the World Military Draft. Being an Admiral, he is easily one of the strongest fighters in the series. Fujitora possesses the Zushi Zushi no Mi, which grants him control over gravity. Koby aspires to reach the position of Admiral and by the look of things, he will definitely reach the level.

9 WILL NEVER BEAT: Monkey D. Luffy

a young luffy is excited about the adventures in store for him One Piece

Luffy and Koby have a history; it goes back to the time when Luffy set out to the sea. Many people consider Koby to be Luffy's equal, but that is just not true. Every meeting between Luffy and Koby has ended in utter disaster for the latter. Luffy will be the strongest character at the end of One Piece, so there's no way that Koby is going to beat him the future.

8 CAN'T BEAT: Scratchmen Apoo

Apoo is a member of the Worst Generation who joined the Animal Kingdom Pirates. Apoo's devil fruit ability is quite unique, and it is almost impossible to dodge any of his attacks. As things stand, Apoo might not make it alive out of Wano.

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With his future looking bleak, it is difficult to imagine that Apoo will reach the same level an Admiral, putting Koby in a position to surpass him.

7 WILL NEVER BEAT: Blackbeard

One Piece Blackbeard

Next up on the list is Blackbeard, who is one of the Yonko. Blackbeard has two very dangerous devil fruits at his disposal. Blackbeard's rise to prominence is truly surreal. He rose to the status of a Yonko in a fairly short period of time. He is the final villain that Luffy is going to face, so it is fair to say that he will be second only to Luffy in terms of power. 

6 CAN'T BEAT: Jinbe

He joined the Straw Hat Pirates after a lot of convincing from Luffy. Jinbe is a fearless fighter and he doesn't back down from a challenge. He was unfazed when he faced Big Mom. Jinbe will undoubtedly play a pivotal role in the Wano arc. Currently, he is stronger than Koby, but things will definitely change as the series goes on.

5 WILL NEVER BEAT: Bartholomew Kuma

Bartholomew Kuma showing his paw to Zoro in One Piece.

Bartholomew Kuma is among the most enigmatic characters in the series. He used to be a member of the Revolutionary Army, and then he joined the Shichibukai. He willingly up his body and became a test subject for Dr. Vegapunk.

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In his prime, Kuma was considered to be a ruthless pirate, which puts him among the strongest Shichibukai (while he had consciousness). 

4 CAN'T BEAT: Dracule Mihawk

Dracule Mihawk One Piece

Mihawk is the current holder of the title of the "Strongest Swordsman in the World." He is without a doubt among the strongest characters in the series. Mihawk has breezed past every opponent. He managed to remain unscathed during the Summit War as well. Mihawk is easily above the level of a Navy Admiral. The fans are eagerly waiting to get a glimpse of his real power. 

3 WILL NEVER BEAT: Sabo

Sabo from One Piece

He is Luffy's sworn brother. Sabo was taken in by Dragon at a very young age. He trained under the Dragon, Ivankov, Kuma, and others. He is one of the best Armament Haki users in the series. In addition to his incredible Haki, Sabo also possesses the Mera Mera no Mi. Sabo managed to fight against Fujitora at Dressrosa. Over time Sabo will have undoubtedly gained better control over his devil fruit. It is rather unlikely that Koby will ever reach the same level as Dragon's right-hand man.

2 CAN'T BEAT: Rob Lucci

Rob Lucci dark expression and Charlos One Piece

Rob Lucci was the main antagonist of Enies Lobby. He ate the Neko Neko no Mi, Model: Leopard, which is a zoan type devil fruit. Lucci is also trained in Rokushiki. Since being defeated by Luffy, Rob Lucci joined the CP-0 and improved his fighting skills. For the time being, Lucci holds the edge over Koby, but it might not last for long.

1 WILL NEVER BEAT: Shanks

shanks one piece

Shanks is the captain of the Red Hair Pirates. So far, Shanks is the only Yonko who doesn't have any devil fruit. He is perfectly capable of using all three types of Haki. Shanks rescued Koby at Marineford. It would not be an exaggeration to say that Koby might not even withstand Shanks' burst of Conqueror's Haki. It is very improbable that Koby will reach the level of a Yonko by the time the series ends.

NEXT: One Piece: Predicting The Top 10 Pirate Bounties After The Wano Arc