Regeneration

Summary
Regeneration is the ability of a being to restore damage caused to it, or to change its physical state to its original state. Regeneration is a skill present in almost everything in the real world, and also extremely common in fiction. There are several types of regeneration, which will be categorized below.

Rank J
Beings with regenerative capacities at the "human" level, but remarkably faster and more effective.
 * Examples: Ryu and Shi-Woon Yi.

Rank I
Beings with the ability to regenerate from wounds that would once leave giant scars.
 * Examples: Dongtae and Twenty-Fifth Baam

Rank H
Beings with the ability to regenerate certain limbs, such as hands, eyes, fingers. Regenerating internal organs, most of the time, also fits here.
 * Examples: Space Marine and [Hashirama Senju

Rank G
Beings with the ability to regenerate lost limbs (e.g. Arms, legs) and serious wounds, but still die from beheading.
 * Examples: Orochimaru and Giorno Giovanna.

Rank F
Beings with the ability to regenerate even from the loss of his head.
 * Examples: Dio Brando and Eren Yeager

Rank E
Beings able to regenerate from being blown up and left to pieces.
 * Examples: Armored City and Hell Joe

Rank D
Beings able to restore themselves from a puddle/drop of blood, or from very small parts of your body.
 * Examples: Cell and X.

Rank C
Beings capable of regenerating vaporization, of being turned into powder, or a similar physical state.
 * Examples: Sun Badguy and Majin Boo.

Rank B
Beings able to regenerate from a single molecule, atom, particle or even smaller, but still existing thing.
 * Examples: Doctor Manhattan and Immortal Phoenix.

Rank A
Beings able to regenerate after having all their material composition erased from existence, but through compositions of other planes of existence, such as the astral plane, is able to reconstitute their entire body.
 * Examples: Reinhard Heydrich and Dark Schneider.

Note
If the being has regeneration at the same speed as a human being, DO NOT put regeneration on your power list. Almost all beings have regeneration, but one should be mentioned in their profiles only those who have a remarkably effective and/or rapid regeneration.