Mihawk is among the strongest pirates in the world of One Piece. He is an excellent swordsman who, after defeating countless others, became the World's Strongest Swordsman. As suited to someone like him, he possesses one of the Saijō Ō Wazamono swords, called Yoru.
Mihawk possesses excellent control over Observation and Armament Haki, making him quite a capable fighter. Given his stature, he is certainly the strongest of all Shichibukai.
Dracul New York is the world's strongest swordsman in One Piece, and his title speaks for itself. His biggest strength is his ability to wield the blade with incredible grace. In the Marineford arc, he showed the fans just a glimpse of his true power and although not everything about his skill is known yet he is someone who rivals the Yonko for sure.
Boa Hancock is the empress of the Kuja Tribe and one of the strongest pirates in the One Piece world. She received her Shichibukai position after just a single voyage to the sea earned her a bounty of 80 million berries.
Hancock is a user of the Mero Mero no Mi, which allows her to turn anyone into stone. She is also a user of the famous Kuja Haki, and can use Conqueror's Haki as well. In Marineford, Hancock wiped out an entire army of Pacifistas and had Sentomaru on the back foot without even breaking a sweat.
Boa Hancock ranks among the strongest women in One Piece. Although the full extent of her powers in combat has not been seen yet, teh fact that she belongs to the Kuja Tribe, who are known for their incredible usage of Haki means that shes very powerful. As such, even though Hancock has a very overpowered Devil Fruit, her Haki should be her biggest strength.
Teach was a member of the Whitebeard Pirates but after stealing the Yami Yami no Mi, he left the crew and created the Blackbeard Pirates. His strength is often underestimated, but he was strong enough to defeat Portgas D. Ace who possessed the powers of the Mera Mera no Mi and had access to two of the Haki types.
What's more, he could even scar Shanks, who is currently a Yonko of the sea. Teach also managed to kill Whitebeard during his time as a Shichibukai.
Teach's time as a Shichibukai showed the fans how far he had planned. His ability to draw out elaborate plans certainly is one of his very best skills. However, his Devil Fruit, the Yami Yami no Mi, is his biggest strength.
Weevil was offered the Shichibukai position after he wiped out a number of Whitebeard Pirates allies. It is unknown what Weevil did during his time as a Shichibukai, however, he certainly does possess monstrous strength.
Kizaru compared his powers to those of a younger version of Whitebeard, which is extremely impressive. Having taken out some of the strongest pirates of the New World, Weevil deserves his rank among the best.
Weevil was the last addition to the Shichibukai before the system was dissolved. Not much is known about him yet, however, the fact that Kizaru compared his powers to that of a young Whitebeard implies that he has tremendous physical strength that rivals the former Yonko.
Donquixote Doflamingo earned the Shichibukai title due to his connections with the World Government and his knowledge of the National Treasure of Mariejois. He used this position to take over the Kingdom of Dressrosa in the New World.
As a fighter, Doflamingo was extremely powerful and had mastered the usage of the Ito Ito no Mi to a point where it awakened. He could also use all the three Haki types, however, his usage of Haki wasn't anything special.
Just like Crocodile, Doflamingo is a mixture of cunning and powerful. Over the years, he put Dressrosa in misery and was so powerful that hardly anyone could oppose him. While Doflamingo was a good user of Haki, his biggest strength was his devil fruit, the Ito Ito no Mi. Doflamingo used this fruit so well that it awakened.
Law became a Shichibukai at some point during the two-year timeskip. He earned the position during the infamous Rocky Port Incident following which he delivered the hearts of 100 pirates to the World Government.
As a Shichibukai, Law proved to be stronger than Smoker and Vergo and quite a match for Doflamingo in battle. His Ope Ope no Mi made him an extremely powerful fighter and he could also use two Haki types with decent proficiency.
Trafalgar Law is one of the strongest Warlords in One Piece, and his time as one of the warlords showed that he was supposed to be reckoned with. Laws biggest ability is his Devil Fruit, the Ope Ope no Mi. His Devil Fruit was worth around 5 billion berries when Law ate it, and he's made its powers his own since.
Kuma was a member of the Revolutionary Army and then became a Shichibukai for unknown reasons. He earned a reputation as the Government's dog over the years, meaning he posed as their most loyal Shichibukai member.
Kuma has the power of the Nikyu Nikyu no Mi using which he can deflect anything at the speed of light. His Devil Fruit power is extremely useful and makes him incredibly difficult to take on in battle.
Kuma was one of the most fearsome members of the Seven Warlords of the Sea, however, now, he is far from his best. Nonetheless, Kuma is extremely powerful and his Devil Fruit, the Nikyu Nikyu no Mi, remains to biggest strength.
Jinbe was offered a spot among the Shichibukai after the death of Fisher Tiger. Having served in Neptune's army and then under Tiger, Jinbe was already plenty powerful and continued to grow stronger.
Over the years, Jinbe has mastered Fishman Karate. He has excellent control over both Armament and Observation Haki as well. Jinbe was strong enough to defeat Who's Who at Wano.
Jinbe is an excellent fighter and his loyalty to those he loves has always shined in the series. Jinbe's biggest power is his mastery of Fishman Karate and Merman Jujutsu. So far, he has the greatest control over these arts that the fans have seen so far.
Crocodile became a Shichibukai at an unknown time and planned to get his hands on the Ancient Weapon Pluton by taking control of Alabasta. With the powers of the Logia-type Suna Suna no Mi, Crocodile could take on some of the strongest people on and he even managed to defeat Luffy twice, losing to him the third time.
After being released from Impel Down, Crocodile appeared to have gotten stronger, as seen when he stopped the likes of Mihawk and even Akainu to some extent.
Crocodile is one of the most impressive figures in One Piece. When it comes to combat, Crocodile's usage of the Suna Suna no Mi remains incredible. His biggest strength, however, is his mind. Crocodile is extremely clever, and fans got to see that in the Alabasta arc properly.
Gecko Moria was once a powerful pirate who even rivaled Kaido back in the day. With time, however, he got weaker and became a shadow of his former self. Moria was still quite impressive in his fight against Luffy. His usage of the Kage Kage no Mi was remarkable but he lacked the power to defeat Luffy, which just goes to show how much he had fallen from grace.
Moria is still a fearsome pirate and although he's way past his prime, he remains to be a menace. Without a doubt, his biggest ability is his clever usage of the Kage Kage no Mi. With its powers, he wreaked havoc in the Florian Triangle for years.
Buggy joined the Shichibukai after the events of the Paramount War. Although he isn't all that strong, he carries great pedigree, being a member of the Roger Pirates and the sworn brother to Red-haired Shanks.
Buggy started his own organization, known as Buggy's Delivery, after being offered the position. Following Doflamingo's fall, he was the greatest source of weapons and trade in the world. However, in terms of power, he isn't all that special.
Out of all the 7 Warlords that fans have been introduced to so far, Buggy remains the weakest. He isn't particularly good at anything, and his Devil Fruit isn't all that impressive either. Buggy's biggest strength so far is being in the right place at the right time, and accidentally rising to power.