The emperors were by definition the strongest pirates in the One Piece universe. Ruling over the high seas with an iron grasp, they were feared by people all across the Grand Line and have the greatest bounties ever issued by the World Government.
While every emperor is fearsome to some degree, they vary significantly in intelligence. Some are conniving masterminds whose full schemes have yet to be realized, while others are so senseless that they need their crew to make important decisions for them. By ranking them, it becomes easier to categorize their likelihood of fulfilling their plans.
7 Big Mom Was Constantly Outsmarted
Despite being the most powerful female pirate in history, Big Mom's intelligence left much to be desired. From childhood through her adult years, she constantly got manipulated into putting her impressive strength toward anyone with the right sentiments.
This was especially seen in Wano, where she turned against the Beast Pirates on two separate occasions. Perhaps Big Mom's worst quality is that she never thinks about the consequences of her actions. When in a hunger pang, she will destroy her own territory until she is sated. This makes her more of an unstable brat than leader.
6 Luffy Almost Never Thinks Before Fighting
Despite the tremendous strides Luffy has taken toward becoming Pirate King, he is extremely temperamental and almost never considers the potential consequences of his actions. He will loudly proclaim himself as Roger's successor regardless of context, resulting in many avoidable fights.
Luffy is also so belligerent that it may come at the expense of his own well-being. For example, he gave almost no thought to attacking Impel Down for Ace and would have died if not for Ivankov and Bon Clay's help. Luckily, Nami helps to reign in his more audacious plans.
5 Buggy Became An Emperor Out Of Luck
Significantly weaker than every other emperor, Buggy only gained his position out of blind luck. However, he clearly isn't stupid; in addition to galvanizing Impel Down's escapees and taking credit for the breakout, he also partnered with Whitebeard at Marineford as an equal.
Further, Buggy was responsible for directing a massive network of mercenaries across the high seas. Therefore, while he might not be the greatest tactician, he has the organizational skills necessary to make the Cross Guild a formidable competitor on the global stage.
4 Kaido's Plans Were Coherent
Kaido proved to be a somewhat decent tactician and organizer. His choice to take up residence on Onigashima was excellent given that the island is highly defendable from invasion. Were it not for Law and Kin'emon, the samurai likely would have never made a full infiltration.
Additionally, Kaido's chain of Devil Fruit production contributed to his ultimate goal of global warfare. Its only significant problem was that if a single link in the chain broke, his entire plan came crumbling down. This was what made Punk Hazard particularly painful for him.
3 Whitebeard Is Wise But Not Cunning
Whitebeard is perhaps the wisest emperor of the sea. He did not pursue the One Piece since he knew that the title of Pirate King was meaningless and only cared for his family and territories. As a result, his crew remained much safer than those of other emperors.
Although able to accurately assess and match enemy forces, Whitebeard does not fare well against treachery. He was completely unprepared for Squard's betrayal, as well as Blackbeard's murder of Thatch. His faith in his children is simultaneously a blessing and a curse.
2 Blackbeard Was Ruthless In His Pursuits
As ruthless as he was ambitious, few could stop Blackbeard once his plans were set in motion. In a single brilliant scheme, he stole Whitebeard's Devil Fruit, leveled Marineford, and even won an entire crew of deadly cutthroats.
The only thing preventing Blackbeard from being rated as the most intelligent emperor is that he is sometimes absent-minded. For example, he let Luffy go at Mock Town since it slipped his mind that he was a target. He failed to correct his mistake when chasing him into Skypiea.
Although Shanks' plans are not yet fully understood, his reputation speaks for itself. So far, he was able to win an audience with the Gorosei and stop the Marineford war all without lifting a finger.
Now that Luffy has defeated two of the biggest power players in the search for the One Piece, Shanks is finally making his move. He knew that if left to their own devices, the emperors would weaken themselves until they were a minimal threat to him. Shanks' opportunistic and low profile methods render him one of the series' most underrated characters.