The users can generate and manipulate the cursed flames of Hell, which can completely destroy anything. The color of the flames varies, but may be black, blue, white, or the normal shades of fire, although probably in some way noticeably unusual. Sometimes, the flames are not generated, but instead summoned from the depths of Hell itself.
Hell-fire can cause excruciating pain upon contact or instead cause instant death, possibly even for relatively beneficial purposes, such as summoning spirits of the deceased temporarily back to the world of living from Hell. Some users can even use Reanimation or Resurrection via Summoning the damned souls of Hell and/or Demons.
A benefit of using hellfire is that, due to its mystical nature and the fact that it tends to attack a person's spiritual essence in addition to their bodies, is that hellfire can be effective against durable targets or people with accelerated healing. As hellfire can attack the spirit or soul, it can inflict injuries that either don't heal or heal very slowly meaning that a critical attack could kill people that heal fast enough to shrug off normally instantly fatal injuries. It can also bypass or damage durable/invulnerable targets by either targeting the spirit/soul or because its magical nature trumps simple physical durability.
Kaen (Jigoku no Gouka de Yaka re Tsuzuketa Shounen. Saikyou no Honou Tsukai to Natte Fukkatsu Suru.)
Naamah (Black Clover) is one of the Highest-Ranking Devils of the Underworld with the ability to cast sinister fire-related spells and manipulate powerful demonic fire using his innate magic attribute, Demon Fire Magic.
Rin Okumura's (Blue Exorcist) Flames of Satan.
Cade (The Vampire Diaries) has the ability to manipulate and create hellfire.
Sabrina Spellman (Chilling Adventures of Sabrina) gained the power to summon and control hellfire from the pits of hell.
Code:Emperor (Code:Breaker) is the originator of the "Seven Flames of Purgatory".
Prime Minister Fujiwara (Code:Breaker) can control the "Seven Flames of Purgatory" because he wields Ogami's left arm.
Mishiru Kokumonji/Kagerou (Code:Breaker) can control the "Seven Flames of Purgatory".
... but has to wear a limiter ring due to the Seven Flames' overly powerful nature being too much as he lost his mastery.
Iskatu (Diablo) can conjure pits of hellfire.
Archviles (Doom) are powerful demons that can command the flames of Hell itself.
Atlas Flame (Fairy Tail) roaring out extremely powerful flames, such that he considers it to be equivalent to the flames of hell.
God Serena (Fairy Tail) as the strongest Wizard Saint possesses 8 different elemental Dragon Slayer Lacrima, one of them is the Purgatory Dragon Slayer Magic.
Natsu Dragneel (Fairy Tail) when he awakened as Zeref's strongest Etherious Demon, can unleashed hellflames powerful enough to burn even a God like Chronos.
Due to his ancestor's blood pact with Orochi, Iori Yagami (The King of Fighters series) can manipulate Orochi's purple hell-fire.
Ghost Rider (Marvel Comics) can manipulate the flames of hell.
Zedonius (Ninja Gaiden series) is one of the Four Greater Fiends and the Malevolent Ruler of Flame. As such possesses the ability to control powerful flames of the underworld.
Monspeet (Seven Deadly Sins)
After being resurrected by Trigon, Slade (Teen Titans) received a small portion of his powers, allowing him control over powerful demonic flames.
Goetia (Valkyrie Crusade) can manipulate demonic fire.
Salamander (Valkyrie Crusade) manipulating blue hellfire.
Hanzo Hasashi/Scorpion (Mortal Kombat)
Hiei (YuYu Hakusho) summoning the Dragon of the Darkness Flames from the darkest pits of Demon World.
Freddy Krueger (A Nightmare on Elm Street)
As the Anti-Christ, Michael Langdon (American Horror Story: Apocalypse) is capable of using hellfire to permanently destroy a soul.
Barbamon (Digimon) can unleashed all of the Dark Area's evil energies at once as a blazing explosion that burns up everything without a trace with its Pandemonium Lost.
Beelzemon X (Digimon) can summon and control the crimson flames of the underworld used to impose judgement upon and offer salvation to the souls of the sinners that fall into the Dark Area.
The Azure Flame (Code:Breaker), also known as Satan Blaze, can burn all physical matter to nothingness. It burns away the sin of wrath. The price to pay for using this flame is the sense of taste.
Belphegor (Code:Breaker), the Black Flame of Limbo, can burn away special powers. It burns away the sin of sloth. The price to pay for using this flame is an internal organ, but a special power may be taken as substitute.
...Mammon, dual colors of green and yellow, are hot and cold, and carries an incredible concussive force that can be highly explosive. It burns away the sin of greed...
...his true form is the Dichromatic Twin Flamberges of the Netherworld, and can be turned into dual blades of the two different colors, which can be used to create whirlwinds via ambient pressure differences.
When uncontrolled, Beelzebub (Code:Breaker), devours life force of all around it, including the wielder. It burns away the sin of gluttony. The price to pay for using this flame is the user's heart will be consumed upon death.
...When controlled, it becomes enter its Seraphim's form, an achromatic flame that can burn invisibly at 1500 degrees Celsius...
...Once gaining complete control of Beelzebub and fusing with it, it becomes the Achromatic Catharsis Flame of Purgatory and the wielder of the Flame of Judgement, which can call forth invisible flames of intense temperature that can disintegrate everything, but the user will suffer recoil of the same intensity.
Leviathan (Code:Breaker), the Argentous Phantom Flame of Hades, is silver colored, and removes the heat from the area to freeze its target, placing it in hibernation state. It burns away the sin of envy. The price to pay for using this flame is the envy of the user's enemies.
Asmodeus (Code:Breaker) traps anyone she burns into an eternal illusion of lustrous dreams, never again to regain consciousness, while assimilating the victim's body into her own, eventually killing them. She burns away the sin of lust. The price to pay for using this flame is the sense of smell, though she can betray a contractor if she is aroused by another...
...his true form, the Iridescence Explosive Flame of Hell, chemically reacts with the surrounding alloy, to create a violently deafening explosion of differing colors.
Lucifer (Code:Breaker), the final of the seventh flame, is an evolved form of the Satan Blaze, controlling and amplifying all other six flames to burn anything, even nothingness, to ashes. The price to pay for using this flame is the user's memories.
Fiendfyre (Harry Potter) is an immensely powerful curse which summon forth enchanted hellflames that can burn and destroyed anything including an intangible soul bounded into a Horcrux.