In the world of One Piece, Blackbeard is the admiral of the Blackbeard Pirates. His path to power is filled with blood and betrayal. After murdering Thatch, Blackbeard obtained the Yami Yami no Mi and left the Whitebeard Pirates. It didn't take long for Blackbeard to form his own crew.
He stole another devil fruit during the Marineford arc, and this time the target was Whitebeard's Gura Gura no Mi. Blackbeard was successful in his attempt, and he became the only person to have two devil fruits in One Piece. One might think that two powerful devil fruits would be enough, but many One Piece fans believe that Blackbeard will get his hands on a third devil fruit. This raises the question, what will be Blackbeard's third devil fruit?
5 Inu Inu no Mi, Model: Cerberus
One Piece creator Eiichiro Oda has a knack for using tales from other mythologies, and Greek mythology has served as the inspiration for many of his ideas. So, it wouldn't be surprising if Oda decided to use another famous creature from Greek mythology in his story.
One of the most popular ideas revolves around Blackbeard being a devil fruit user even before he stole the Yami Yami no Mi. It is possible that Blackbeard consumed the Inu Inu no Mi, Model: Cerberus, a Mythical Zoan-type devil fruit. Since Cerberus is known for having three heads attached to the same body, it would explain how Blackbeard managed to eat two more devil fruits, one for each head. This idea is definitely intriguing, and it also makes sense as Blackbeard's Jolly Roger consists of three skulls.
4 Ope Ope no Mi
The Ope Ope no Mi is a Paramecia-type devil fruit that was eaten by Trafalgar Law when he was still very young. The devil fruit has been labeled the "Ultimate Devil Fruit" by Donquixote Doflamingo. The Ope Ope no Mi allows Law to create ROOMs in which he has complete control over every object.
Law displayed the power of the devil fruit's awakening in the Wano Country arc. The last time fans saw Law, he was engaged in a battle with Blackbeard. Given the Yonko's strength, it is reasonable to expect him to win the fight. After winning, Blackbeard will definitely take the Road Poneglyph rubbings and maybe even Law's devil fruit. Alternatively, it is possible that Blackbeard might force Law to use the Immortality Operation to prolong his lifespan. Either way, Trafalgar Law is in serious danger if he loses to Blackbeard.
3 Mero Mero no Mi
The Mero Mero no Mi is the devil fruit of the former Shichibukai, Boa Hancock. She was forcibly fed the devil fruit by the Celestial Dragons for their amusement. They were under the impression that Hancock and her sisters would never leave Marijoa, so they did not care about what devil fruits they were feeding the three sisters.
Over time, Boa Hancock mastered her devil fruit, and it became one of her strongest weapons. The Mero Mero no Mi is a special devil fruit that can petrify people and objects. In the manga, it was revealed that Blackbeard and his crew attacked Amazon Lily to steal the devil fruit. Hancock was extremely lucky that Rayleigh was present on the island to de-escalate the situation. The possibility of Blackbeard returning in the future remains small, but it would be foolish to rule it out completely.
2 Uo Uo no Mi, Model: Seiryu
The Uo Uo no Mi, Model: Seiryu belongs to Kaido of the Beasts Pirates. The devil fruit was given to him by Big Mom when they were both on the crew of Rocks D. Xebec. It is a mythical Zoan-type devil fruit that grants its user the ability to transform into a massive Azure Dragon.
The reasoning behind the possibility of Blackbeard taking Kaido's devil fruit is quite simple: it is arguably the strongest Zoan-type devil fruit in the series. Of course, there is Luffy's Hito Hito no Mi, Model: Nika, but Oda cannot send Blackbeard after the protagonist just to steal the devil fruit. So, the next logical choice would be to go after Kaido. As of now, Blackbeard has the strongest Logia and Paramecia-type devil fruits; therefore, the third devil fruit will have to be the strongest in the Zoan category. It also seems a bit strange that Blackbeard invited Moria to join his crew during the Wano Country arc. Considering Moria has a past with Kaido, it adds more fuel to the possibility of Blackbeard going after Kaido's devil fruit.
1 Tako Tako no Mi, Model: Kraken
It may seem outlandish to think that Blackbeard might have a devil fruit that allows him to transform into the scary Kraken, but there are certain things that make sense about this idea. The Kraken has been primarily depicted in popular literature as a massive octopus or squid capable of easily destroying ships. This creature has enough power to overwhelm a ship and drag its crew to the deepest corners of the sea.
Octopuses have three hearts, and the number three has been heavily associated with Blackbeard. If the Yonko has this devil fruit, it is possible that he also has three hearts, allowing him to consume more than one devil fruit. Furthermore, Blackbeard has already been established as the only character who accurately represents real-life pirates, and the Kraken was often included in their stories about the horrors of the sea.