One Piece is an epic shonen series that has been written by Eiichiro Oda. It is the most popular manga series in the world, and it has sold over 500 million copies worldwide. The biggest highlight of the series is its complex world-building, and it never ceases to amaze the fans.
However, this does not mean that the other aspects of the series are bad. In fact, there are some fans who are more fond of other traits such as the myriad of characters. Oda has created all kinds of characters, including some very scary ones. These characters are designed in such a way that they scare their opponents and One Piece fans as well.
7 Blackbeard
Currently, Blackbeard is one of the Four Emperors of the Sea. He managed to gain a spot in the elite group after defeating the remnants of the Whitebeard Pirates. By nature, Blackbeard is a very evil person, who does not hesitate to use underhanded means to accomplish his goals.
When he was still an underling on Whitebeard's ship, he killed Thatch in cold blood. Afterward, he captured Ace and handed him over to the Marines. The power of his Yami Yami no Mi allows him to engulf anything that he wishes, which makes him a fearsome character.
6 Doflamingo
Driven by his evil charisma, Doflamingo is one of the best villains that the series has witnessed to date. Normally, Doflamingo does not seem scary, but once the veins on his forehead started to emerge, that's a sure sign that the other person is in trouble.
Perhaps what makes Doflamingo scary is his maniacal laugh, which he uses almost every single time. With his devil fruit, Doflamingo was able to control the movement of other people, and he used this power to take over the country of Dressrosa. The scariest thing about his reign was that most people were completely unaware of the fact that they were living under the rule of a tyrant. In addition to this, Doflamingo worked as a broker in the Under World where he sold devil fruits, weapons, and even people.
5 Big Mom
There are hardly any sights in One Piece that are more terrifying than an angry Big Mom confronting her opponent, and asking them a simple, yet scary question—Life or Death? In addition to acting as a trigger for his devil fruit, it also scared the living daylights out of her opponents.
Big Mom's short temper made it very difficult for any of her family members to even talk to her. In fact, when she was angry, Big Mom would not even spare her own kids, and she would even kill them if she wanted. Needless to say, a person who can kill their own children is definitely terrifying.
4 Bartholomew Kuma
Bartholomew Kuma is a former Shichibukai, who has been turned into a mindless cyborg by Dr. Vegapunk. After losing his ability to think, Kuma was used as a personal slave by one of the Celestial Dragons. Presently, things might look good for him, but it wasn't always bad for Kuma. In the past, Kuma used to be a world-renowned pirate.
When Kuma appeared at Thriller Bark, all the members of Moria's crew were frightened by his mere presence. Kuma barely spoke, but the way he carried himself made him appear quite threatening. Kuma's reputation became worse when he fought against the Straw Hat Pirates on Sabaody Archipelago. Kuma overwhelmed the crew very easily and sent them to different places. The fans were taken aback because they had never seen the crew crushed before.
3 Akainu
Akainu is the Fleet Admiral of the Marines, a position that he attained after beating his fellow Admiral, Aokiji, in a battle on Punk Hazard that lasted for ten days. Akainu is the most ruthless Navy Admiral, as seen in the Marineford arc where he killed Portgas D. Ace.
Aside from being powerful enough to crush his opponents, Akainu also uses manipulation to turn people against each other. There are several incidents that prove his status as one of the scariest characters: first, when he killed another Marine; second, when he attacked Koby; and finally, when he destroyed the ship carrying Ohara's citizens.
2 Kaido
Kaido was known as the "Strongest Creature in the World." From a young age, Kaido's power impressed his comrades, and they were wary that he could pose a threat to the people around him, so they tried to sell him to the Navy. As he grew older, Kaido won the respect of other people with his strength. His first appearance in the series was a truly incredible sight as he crashed onto an island, but emerged with no injuries. Seeing Kaido standing before him was enough to strike fear into the heart of the intrepid Eustass Kid.
Kaido's goal was to start a war that would engulf the entire world. To achieve this dream, he commissioned Doflamingo to produce SMILEs, which he fed to his soldiers. Kaido did not care about his soldiers and he would willingly kill them if they angered him. Kaido's tyranny almost destroyed Wano, and it took a massive alliance to take him down.
1 Magellan
Magellan's reputation might be tainted because he spends so much time on the toilet, but it doesn't make him any less scary. He is a very powerful character, who is endowed with the power of the Doku Doku no Mi. The devil fruit allows him to create all types of lethal poisons that he can use against his opponents.
When enraged, Magellan uses his devil fruit to create a devil-like entity, which is covered by a crimson-colored poison, known as Kinjite. This is Magellan's most potent poison, and it can even affect inanimate objects such as stones. When the Impel Down escapees saw this form of Magellan, they were petrified, and they accepted that they were going to meet their end.