Free (Soul Eater), The Man with the Demon Eye, Werewolf from the Immortal Clan.
Possess "true" immortality
The power to be eternal and indestructible. An advanced version of Immortality.
The user possesses absolute immortality, unable to die, get sick, or be permanently wounded, and, as the user's mind and soul are as immortal as their biological bodies, they are immune to mental damage. Any injuries the user suffers immediately heal, even if the user's body is disintegrated or blown up or completely deleted, even if the user is completely destroyed to the sub-atomic level, they will still return to life. Alternatively, some users are absolutely immune to all harm, nor can they die of any natural causes.
Also, the power cannot be removed, rendered truly perfect and absolute.
As agent of the Elder God, Raziel (Legacy of Kain) is beyond death.
After fusing with the Hogyoku, Sosuke Aizen (Bleach) gained both immortality and indestructibility.
Kaguya Houraisan (Touhou) gained this power after drinking the Hourai Elixir.
After making a wish on the Dragon Balls, Garlic Jr. (Dragon Ball) does not age and regenerates any and all bodily damage.
Thanos (Marvel) was banned by Death itself from entering its realm, and thus is unable to die in any way
Being a supernatural entity of immense power, Fanoxean (The Young Guardians) is virtually impossible to kill in any way.
Porky Minch (EarthBound) being trapped in the current timeline due to his abuse of time travel, cannot age nor die in anyway. He lived to the end of the world, and is still alive.
Deadpool (Marvel) has one of the most powerful healing factors in the world and was cursed to live eternally by Thanos.
Silas (Vampire Diaries) was transformed into a true immortal once he'd drank the Immortality elixir. He is immune to all weapons, except for the cure for immortality.
Sailor Cosmos (Sailor Moon) is the Sailor Moon's final form, she reached this level by unknown factors. She is considered to be a true immortal.
Bolt Crank's (Eat-Man) immortality is so absolute that even Death himself is unable to effect him in any way.
The Four Horsemen of the Apocalypse (Supernatural) are absolutely immortal so long as the concept they represent exists
Benares (3x3 Eyes) is a Wu, an absolute immortal who has had there soul removed, as such he is completely immortal and unkillable even surviving and regenerating from the complete destruction of his body.