Doflamingo and the Dark Fruits of One Piece’s Power

Doflamingo, the ruler of Dressrosa and the former Warlord of the Sea, has devoured the Ito Ito no Mi. This fruit allows him to control and create strings from his own body. Doflamingo even awakened the dark potential of his abilities.
However, Doflamingo did not develop Haki properly, a crucial disadvantage during his battle against Luffy. This shortcoming played a significant role in his eventual defeat against the main character.
Jack and Zou Zou no Mi, Model: Mammoth

Jack is one of the stars of the Beast Pirates. The ancient Zoan fruit that Jack consumed allows him to transform into a mammoth, granting him extraordinary physical strength. However, Jack is relatively weak in other combat aspects. His Haki has not developed adequately, making his immense strength heavily reliant on the powers provided by his fruit.
Ace and Mera Mera no Mi

Ace is one of the most renowned pirates of the current era. He consumed the Logia-type Mera Mera no Mi, which grants him the ability to control fire. Despite having the potential to master all three types of Haki, Ace’s reliance on his devil fruit is clear, limiting his overall potential in battles.
Crocodile and Suna Suna no Mi

The former Warlord of the Sea, Crocodile, is known for his ability to manipulate sand through the Suna Suna no Mi. He can control this devil fruit’s powers exceptionally well, showcasing his strength. However, Crocodile focuses too much on his sand powers and neglects to train other essential combat skills.
Eustace Kid and Jiki Jiki no Mi

Eustace Kid is a notable member of the Worst Generation. He has consumed the Jiki Jiki no Mi, which allows him to manipulate magnetic forces. Kid can even channel the dark powers of his fruit to enhance his combat abilities. However, he primarily focuses on his raw strength rather than mastering Haki.
Trafalgar Law and Ope Ope no Mi

Trafalgar Law is another prominent figure known for his formidable strength and skills, credited to his Ope Ope no Mi abilities. Despite being capable of mastering Haki, his reliance on his devil fruit remains significant, especially after events in Wano and the battle against Kaido.
Kizaru and Pika Pika no Mi

Kizaru, one of the Marine Admirals, possesses the light-based Pika Pika no Mi. He often relies on his devil fruit powers during battles, rarely using Haki. This limitation has hindered his potential in combat situations.
Big Mom and Soru Soru no Mi

Big Mom heavily relies on her Soru Soru no Mi abilities. Although she has the potential to master Haki, including advanced forms, she tends to focus more on the powers of her devil fruit. In her battle against Kid and Law, the story emphasizes her raw strength derived from her fruit rather than her Haki capabilities.