Ever since the start of the Great Pirate Era in the One Piece world, pirates have taken the seas by storm. The era has become a lot more turbulent and, as such, the Navy has faced quite a lot of difficulty in attempting to control the influx of their kind.
To remedy that, they started issuing huge bounties on the heads of pirates and other criminals alike. This would attract other people to do their work for them and turn the criminals in for the massive bounties on their heads. These people are known as bounty hunters and, over the years, a few have appeared in the series, some more important than others.
8 Johnny
Johnny was revealed to the fans shortly prior to the event of the Baratie arc of One Piece. It was mentioned that he used to work with the Swordsman of the Straw Hat Pirates, Roronoa Zoro long ago.
Johnny is known to have been a decent bounty hunter, however, he mostly operated in the East Blue where he got small-time pirates and other criminals for smaller rewards. Johnny is not all that powerful and is certainly among the weakest bounty hunters seen in One Piece to date.
7 Yosaku
Yosaku is Johnny's best friend and was revealed to the fans with him prior to the events of the Baratie arc. Just like his brother, he is a bounty hunter and collects smaller rewards instead of going for the big names. Over the years, he has been successful in this endeavor to an extent, however, he certainly isn't one of the most famed bounty hunters in the One Piece world.
Yosaku is also skilled with the blade to an extent, however, when compared to the other bounty hunters, he certainly is rather weak. He played a decent role in the Baratie and the Arlong Park arc, after which he and his best friend went their own way and the Straw Hat Pirates headed to the Grand Line.
6 Miss Wednesday
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Miss Wednesday was introduced to the fans immediately after the Straw Hat Pirates entered the Grand Line. When the crew met Laboon, Miss Wednesday attempted to capture the beast and take it back with her to Whiskey Peak. Soon, the crew found their way to Whiskey Peak as well, where the true allegiance of Miss Wednesday was revealed to the fans.
At first, it was made known that Miss Wednesday is a bounty hunter, just like the many other members of Baroque Works who worked under the mysterious Mr. 0. Later, it was revealed that Miss Wednesday was actually the Princess of the Alabasta Kingdom and had infiltrated Baroque Works in order to find out the true identity of the man trying to run her country into the ground.
5 Zoro
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Zoro is the swordsman of the Straw Hat Pirates and one of the main characters of One Piece. He aims to become the strongest swordsman in the entire world by defeating Dracule Mihawk, the person who currently holds this title. Zoro is incredibly powerful and although he is a pirate right now, he was once a pirate hunter. After he left the Shimotsuki Dojo in the East Blue, he served primarily as a bounty hunter and that's how he made his living.
After he was saved by Luffy, Zoro was forced to join the Straw Hat Pirates and, ever since then, he hasn't looked back. During his bounty hunting days, he wasn't all that powerful, yet was a name that pirates feared in the East Blue.
4 Daz Bones
Daz Bones is known to have been a former bounty hunter in the West Blue. At some point in his life, he joined up with Sir Crocodile of the Baroque Works and served as Mr. 1 of the organization, making him the strongest subordinate of Crocodile. He possesses the powers of the Supa Supa no Mi with which he has become a dice human and can produce blades from any part of his body.
Mr. 1 is an incredibly powerful fighter and his skill in battle was seen when he was able to overpower Zoro of the Straw Hat Pirates with rather ease. As a bounty hunter, he would certainly have been extremely efficient as well.
3 Jean Ango
Jean Ango was introduced to the fans during the Dressrosa arc and, just like Abdullah and Jeet, he was also one of the participants fighting for the Flare Flare Fruit in the Corrida Colosseum. There, it was revealed that he is quite a successful bounty hunters and that he had even targeted the escapees from the Impel Down prison.
Over the years, he has sent several of the escapees back to Impel Down once again and he attempted to fight Luffy for the same reason. In the end, he proved to be not all that powerful and his threat was rather tame. Luffy managed to deal with Jean Ango pretty easily.
2 Abdullah And Jeet
Abdullah and Jeet are two characters that fans were introduced to during the Dressrosa arc when the fight for the Flare Flare Fruit was going on in the Corrida Colosseum. It was revealed to the fans that both of them were former bounty hunters and that they were involved in quite a few massive events, such as the bombing of the World Government.
Abdullah and Jeet are known to fight together and attack in tandem. In the Colosseum, they put on quite a show, however, they were certainly not strong enough to win the whole thing. To the elites, they were merely flies.
1 Franky
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Franky is the Shipwright of the Straw Hat Pirate crew, however, just like Zoro, he used to serve as a bounty hunter in the past. In his case, he was more of a dismantler and would get money from any source that he could find. Franky often saved the people of Water 7 from vicious pirates by posing as a member of the Underworld of the country.
By beating them up and turning them in, he also earned quite a lot of money. Franky later ended up joining the Straw Hat Pirate crew after the events of the Enies Lobby arc, as it became clear that he could not stay safely on the island anymore.