Healing factor

A healing factor is a term used to describe the ability of some characters in fiction to recover from bodily injuries or disease at a superhuman rate. The term itself is most commonly applied to comic book characters in the Marvel Universe, although other quickly-regenerating characters exist.

Artistic license
The efficiency of a character's healing factor, as with all "powers", varies frequently, depending on the situation and the writer writing it, with, as a story is being told, drama being the key factor (one example is Agent Zero, who uses a special acid that temporarily negates the subject's healing factor).

Broad displays of artistic license have often led to debates among fans of particular comic book characters that have superhuman rates of healing, such as Wolverine, Deadpool, Sabretooth, Hulk, et cetera, as to which comic characters heal faster, or what the ultimate extent of their healing factors might be.

Marvel Comics
There are numerous characters within the Marvel Universe that possess some form of accelerated healing ability. The source of these "healing factors" ranges from genetic mutation to artificial enhancement to magic. The exact limits of some character's healing powers is often a source of debate among fans since many of their healing powers have appeared to fluctuate in efficiency.

Marvel Comics characters known to possess a "healing factor" include:

Ultraverse

 * Sludge

DC Comics

 * Amazo
 * Connor Hawke
 * Creeper
 * Deathstroke
 * Doomsday
 * Flash
 * General Wade Eiling
 * Hawkgirl (All versions due to Nth Metal)
 * Hawkman (All versions due to Nth Metal)
 * Hawkwoman (All versions due to Nth Metal)
 * Hourman
 * Icon
 * Knockout
 * Kryptonians (Provided they are exposed to or possess a charge of energy from a yellow sun or similar forms of energy)
 * Lobo
 * Manhunter (Both Paul Kirk and his clones)
 * Martian Manhunter
 * Misfit
 * Orion
 * Shaggy Man
 * Solomon Grundy
 * Supergirl
 * Superman
 * Swamp Thing
 * Vandal Savage

Wildstorm

 * Daemonites
 * Grifter
 * Voodoo

Topcow Comics

 * Witchblade

Image Comics

 * Hellspawn
 * Malebolgia
 * Tremor

Valiant

 * Bloodshot
 * Rai

Outside of comics
Non-comics characters who can heal rapidly in one manner or another include:
 * Adam Baylin
 * Adam Monroe
 * Adric
 * Alchemy Warriors using their kakuganes
 * Alexander Anderson
 * Alice
 * Alien Bounty Hunter
 * Alucard and other vampires
 * Angels
 * Arthur Petrelli, after contact with Adam Monroe
 * Arvin Sloane
 * Boris Tepes Dracula
 * Cell
 * Chimera Ants
 * Chiropterans
 * Claire Bennet
 * The Creeper
 * Crusniks
 * Dante
 * Demons and Angels
 * Dorian Gray
 * Elder Toguro
 * Evangelion Unit 01 after devouring the fourteenth angel's S² Engine.
 * Freddy Krueger
 * Godzilla
 * Grim Reapers
 * Gua
 * Hollows (only Menos and Gillian Class can regenerate)
 * Hugo Danner
 * Homunculi
 * Imhotep
 * Immortals from the Highlander television series and films
 * Isabelle Tyler
 * Jack Harkness
 * Jasmine
 * Jason Voorhees
 * Jenova
 * Jin Kanzaki/ZET
 * Kevin Burkhoff
 * Koshaku Chono and his fellows Homunculus
 * Lestat de Lioncourt and other vampires
 * Lucifer Hawks
 * Majin Buu
 * Manji thanks to the Kessen-Chu
 * Max Evans
 * Methuselah
 * Mina Harker
 * Minoru Kamiya
 * Naruto Uzumaki
 * The Orks
 * Peter Petrelli via contact with Claire Bennet
 * Piccolo and other nameks
 * Players
 * Prometheus, of ancient Greek myth, who regenerated his liver after it was daily torn out by an eagle during his punishment.
 * Sadako Yamamura
 * Sam Isaacs
 * Saya Otonashi
 * Slayers, Vampires, Demons, and Werewolves from The Buffyverse.
 * Super Soldiers
 * Sylar
 * Tatsumi Saiga
 * The Twins
 * Trolls from the role playing game Dungeons & Dragons
 * Vampires, Lycans, Hybrids and True Immortals from the Underworld films
 * Vergil
 * Vincent Valentine
 * Werewolves, unless confronted with silver
 * Willow Rosenberg
 * Yakushiji Tenzen