Top 6 Almost Immortal Characters in One Piece

BROOK

While he was still alive, Brook ate the Yomi Yomi no Mi, a Paramecia-class Devil Fruit that allowed his soul to return to his body after he died. This allows him to reside within a skeleton body, and he can even perform the functions he did when his body contained flesh and muscle.
So Brook isn’t concerned by the flowing of time because he can’t get older and, for this logic, he can’t reach an age in which he should be assumed to die.

IVANKOV

Ivankov ate the Horu Horu no Mi, which allows him to control the hormones of the human body, and is one of the very few known powers coming from a Devil Fruit that can affect other people’s bodies as well as his/her own. This power led him to be known as the “Miracle Person”.
He can remodel a human from the inside, which allows them to change all physical aspects, including: sex, growth, skin pigment, and many other things.
This also allows him to boost a person’s chances of survival from conditions that would otherwise mean certain death.

JEWELRY BONNEY

Bonney exhibits unexplained abilities that appear to come from a Paramecia-type Devil Fruit that involves age manipulation. She can alter the ages of herself and others, rapidly aging her intended targets into their senior years or regressing them into small children. As a result of this ability, age can’t kill her.

TAMAGO

Tamago ate the Tama Tama no Mi, an unclassified Devil Fruit that turns his body composition into that of an egg. When his body is broken, Tamago evolves into a stronger form that gradually loses his human appearance and gives him the appearance of a chicken each time he does so. He has three forms, Baron Tamago being his base form, Viscount Hiyoko, and Count Niwatori. He is stated to become stronger in combat each time he evolves, and is a “true knight” once he reaches his third form. Should his strongest form be destroyed, he reverts to his weakest base form. This endless cycle effectively prevents him from dying in battle.

MARCO THE PHOENIX

Marco ate a Devil Fruit referred to as a Mythical Zoan type, an immensely powerful type of Zoan Devil Fruit, said to be the rarest type, even rarer than Logia fruits. While this fruit’s power is classified as a Zoan, due to the uniqueness of the phoenix itself, the additional powers it grants may be considered similar to those of Paramecia (the somewhat “superhuman” power that affects the user’s body: regeneration) and Logia (the generation of blue phoenix flames).
The fruit’s greatest attribute, however, is that by transforming into a phoenix of blue flames at will, Marco can regenerate any wounds with the blue fire he generates, much like how a phoenix is said to rise from its own ashes. These blue flames are what allow him to heal, and are referred to as the “Blue Flames of Resurrection”.

KAIDO

As one of the Yonko, Kaido is among the strongest pirates alive, renowned as the “Strongest Creature in the World”. He attempted to take Whitebeard’s life, something few would dare, and subsequently clashed with Shanks. When Gekko Moriah was in his prime, Kaido fought him and emerged victorious, having killed his entire crew.
Perhaps the greatest sign of Kaido’s strength is his apparent inability to die due to his tremendous toughness and durability. He has been caught and tortured 18 times, and people as powerful as the Marines and other Yonko have attempted to execute him 40 times only to fail as Kaido survived every single attempt because every single execution weapon broke when being used on him. Most notably, Kaido has jumped from 10,000 meters from the sky onto the ground, creating a massive shockwave strong enough to sink a large ship nearby, and emerged only with a headache; it has even become a hobby for him to attempt suicide, only for it to fail.