Summary
The story of One Piece is often presumed to be full of humor, which is why many people believe that there are no serious elements in the series. However, the story covers several dark themes, including betrayal.
Aside from the Straw Hat Pirates, most of the privateers in One Piece are just dangerous criminals who are willing to kill and maim others for their pleasure. Naturally, it is not hard for these characters to betray their crew members. Each betrayal had different consequences, with some even leading to the annihilation of a particular crew.

5Nami
Broke The Trust Of The Straw Hats
Nami is the navigator of the Straw Hat Pirates. She decided to join Luffy and Zoro in the Orange Town arc, and she stuck by their side until the Baratie arc. Nami found a bounty poster that had Arlong’s picture on it. This changed her mood completely, and she decided to head back to her home.
Nami left Baratie without informingany of the Straw Hatsof her plan. When they learned about her whereabouts, they wasted no time in pursuing her. However, they did not hurt Nami. Instead, they decided to help her by beating Arlong and his goons. Following their victory over Arlong, Nami was free to rejoin the Straw Hats. While her betrayal did not hurt any character physically, it did raise a lot of questions about the relationship between the Straw Hats. Presently, Nami is an integral part of the crew, and she is willing to sacrifice herself for the sake of her captain.

4Squard
Stabbed Whitebeard
Squad was introduced in the Marineford arc, where he foughtalongside the Whitebeard Pirates. Their aim was to free Portgas D. Ace and take him home safely. However, the Marines were not willing to stand idly by and let Whitebeard take back one of his sons.
This led to a war in which both sides lost many people. The Marines had the edge for the most part as it was their turf, and they had the time to prepare in advance. When the Whitebeard Pirates refused to let up, some of the Marines resorted to underhanded tactics. Admiral Akainu tricked Squard into believing that Whitebeard was just using his allies. When Squard was close to Whitebeard, he took the opportunity to stab his captain. Whitebeard was injured, yet he did not retaliate. Instead, he hugged Squard and made the latter understand, that to him, every crew member was the same. This made Squard realize his mistake, but the damage was already done.

3Donquixote Rosinante
Collected Information On His Brother
Donquixote Rosinante, better known as Corazon, was the youngest son of Homing. Corazonwas a Celestial Dragonby birth, but his father decided to discard his title and live a normal life. This decision proved to be a massive disaster, as it led to the death of Corazon’s mother. Furthermore, it caused Doflamingo to become completely berserk and kill his father. Corazon would have been spoiled under Doflamingo, but thankfully he was taken away. Corazon spent a lot of time under Sengoku’s care, which helped him blossom into a splendid human being.
He stayed true to his principles and didn’t change even a bit. As he grew up, Corazon joined his brother’s crew to report his findings to Sengoku. Unfortunately, all the information that he had gathered landed in Vergo’s hands. Doflamingo was certain that his brother had betrayed him. So, he had zero hesitation while killing Corazon.

2X-Drake
Joined Kaido’s Crew Only To Betray Him
X-Drake was a Rear Admiral working for the Marines. Originally, he was working for his father, who was abusive towards him. X-Drake’s father was confident in his son’s power, and he believed that he could count on him in times of need. However, when Doflamingo attacked Diez Barrels, X-Drake ran away.
After he joined the Marines, X-Drake rose through the ranks and became one of the top officers. At some point,he joined SWORD anddecided to go undercover. X-Drake impressed Kaido and became a Tobi Roppo. He stayed loyal to the Yonko until Luffy and his friends raided Onigashima. X-Drake took this opportunity to betray Kaido and help Luffy.

1Blackbeard
Murdered His Captain And Crewmate
Blackbeard may be a Yonko now, but there was a time when he was nothing more than a regular fighter on Whitebeard’s crew. He decided to join the crew and laid low so as to not attract any unwanted attention. This continued for years until, one day, Thatch found the Yami Yami no Mi. Blackbeard had been waiting for years to get his hands on the Devil Fruit, so when his crewmate found it, he knew what he had to do. Blackbeard murdered Thatch andstole the Yami Yami no Mi.He then ran away and started his own crew.
Blackbeard’s betrayal didn’t end there. He defeated Ace and handed him over to the Marines in exchange for a place among the Shichibukai. Later on, he went to Marineford, where he killed Whitebeard, the man who had sheltered him for years. Once Whitebeard was dead, Blackbeard somehow stole his Gura Gura no Mi. Needless to say, this is one of the biggest betrayals inOne Piece.
