Hiei from YuYu Hakusho has two attacks that are comprised mainly of hellfire. The first is Fist of the Mortal Flame, which uses the fire from human hell to pummel the opponent. The other, much more dangerous attack is Dragon of the Darkness Flame, which is an enormous dragon made of flames from the demon hell.
Theories that it summons fire from hell aside, Amaterasu from Naruto doesn't have any connection to hell, but exhibits many traits as hell fire: special color (black), extremely hot (supposedly as hot as the sun), has impossible properties (can burn non-flammable objects, even underwater & can cause even Bijuus who shrug off lesser attacks to cry out in pain), and is very hard to put out (can't be put out unless you wait for a week, seal it, or the user snuffs it out).
Zetsu actually says at one point that Amateratsu is supposedly "black hellfire". It's real nature is never clarified.
The tailed beasts' chakra isn't really fire of any sort, but when a Tailed Beast's host put out enough of the chakra, it can incinerate anything it touches... even the host himself.
In Slayers, there's a distinction: for example, Fireball is Shamanism spell — it calls upon fire spirit. Gaav Flare, on the other hand, was Black Magic using the power of Chaos Dragon, one of Dark Lords. Defunct after Gaav's demise, of course. Reflecting Gaav's nature and power level, it's much nastier and burns through the first target, then whoever was behind it...
Unless this is a variation between manga and anime, he used Exodus to take out Efreet. And he created a fire that was hotter than the sun by harnessing the heat of Efreet's own fire spells. With a nice middle finger to Convection Shmonvection, the room made of stone is actually melting. BEFORE this "fire hotter than the sun" was created. And the actual proper name of his ultimate spell is "Helloween", after the band. The anime changed some of the spell names for fear of copyright issues. Such awesome spell names included are "Poison, Megadeath, Guns & Roses, etc". It's a post apocalyptic fantasy manga with a LOT of rock references thrown in.
In Blue Exorcist, blue flames are the sign of Satan. Rin, a son of Satan, tends to erupt into them. This is a problem due to Fantastic Racism and also a boon; there isn't much that can handle them after they are the only demonic flames that attack the physical and the spiritual.
Shima can summon a demon that uses black hellfire.
Zancrow summons and controls pitch-black flames that can burn and injure Natsu. Natsu is normally immune to heat and eats flames. Natsu eventually manages to eat Zancrow's flames, giving him the power boost to defeat him.
The dragon Atlas Flame describes his flames as hellfire.
"Ah, good old hellfire, when regular fire simply won’t do."
Fantastic Four example: Doctor Doom opens a portal to Hell, and Johnny and Franklin are pulled inside. Johnny gets out, but not without being badly burned; especially notable considering he's the Human Torch, master of flame in all forms, who hasn't suffered a burn in, like, thirteen years. Yeah. Hellfire. It'll mess you up.
Though Johnny later finds out that the holy flames of an archangel's Flaming Sword are even more painful.
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHH grants Harry Potter the power to wreathe his fists in "Holy Fuckfire" with which he punches the heads off vampires, sending them into the past of Mars, or... something. Notable for being evidently a holy force rather than an infernal one, and... powered by swearing, or something.
Poké Wars depicts Will-O-Wisp in this form. It is a sinister dark purple/blue flame that ignites anything it touches and cannot be extinguished.
While not specifically from hell, fiendfyre in Harry Potter is hot enough to destroy a horcrux, something which is rather difficult to do. And is sentient. And malevolent. And a lot harder to put out than to start. And very difficult for a normal wizard to control, so it's not like you can practice with it.
After demonic shadow who gives him access to hellfire dies saving Harry's life he finds out that the archangel in charge of maintaining free will, and God's own holy hitman, Urielnote The one who killed all of Egypt's firstborns has gifted him with Soulfire, the fires of Creation itself. It fits the trope just as well as normal Hellfire - it makes the spells more "real," and thus more powerful, but at the cost of some of Harry's soul (though it regenerates so long as he has some left. It regenerates more quickly if he takes time to nurture it; for example, going on a date with Luccio at the end of Small Favor). The Soulfire also burns an unusual color - it usually adds a bit of a silver tinge, depending on how much he uses and what spell he ties it to.
There's also Summer Fire, a gift granted by the Summer Court. So far, though, it's only been used against its polar opposite in the form of the Winter Fortress, where it is understandably extremely destructive, so no word on if it's actually any hotter or more powerful (though it does leave a trace in the user's fire magic from then on).
It was theorized that Dragon's Fire would be sufficiently hot, but there weren't any more dragons...D'oh!
Dragonfire could destroy the lesser Rings of Power (the Three, Seven and Nine), and in fact that's what had happened to some of the Seven Rings of the Dwarves), but Gandalf says that not even the fire of Ancalagon the Black (the greatest of all dragons) could destroy the One Ring.
In the Betsy the Vampire Queen books by Mary Janice Davidson, the titular queen's half sister Laura is the daughter of Satan (don't ask). As such, one of Laura's powers is to summon a sword made of hellfire. It can transform into a crossbow in the blink of an eye, and is implied to always be hanging at Laura's hip, invisible when she doesn't need it. Hellfire only disrupts magic, so it passes harmlessly through mundane humans but incinerates vampires instantly. However, Betsy's odd status as Queen of the Dead means that the sword neither passes harmlessly through nor incinerates her, but stabs her like a normal sword would. It gets stuck and must be pulled out, but leaves no wound behind.
Referred to as 'Wizard's Fire' in Sword of Truth. It's described somewhat like a magical version of napalm, a "liquid flame" which won't be put out by smothering, even if it's just a little bit of flame; in fact, it will just set on fire whatever you use to smother it. Beyond that, an even stronger version known as Wizard's Life Fire appears at a few points, used as a Desperation Attack by wizards who are about to die anyway.
The science fiction novel Roadside Picnic mentions a substance called "Witch's Jelly", left behind by the mysterious alien visitors, that will burn (or corrode?) through just about anything, leaving a flaming pit in the ground as it goes.
A Song of Ice and Fire has wildfire and dragon's breath. Wildfire is the exclusive creation of the Alchemist's Guild, a liquid something like magical napalm which burns with an intense green flame that's impossible to extinguish (it can burn water!), and seems to be almost alive in larger conflagrations. It seems to be based on Greek fire. Dragon's breath is apparently much hotter than normal flames, and is said to possess magical qualities, such as its use in the creation of Valyrian Steel.
Science Fiction variant in Charles Stross' Glasshouse - "Blasters" are very simple weapons based around a couple of wormholes. One end opens at the end of your pistol; the other opens into a sun.
A certain spell in Chronicles Of The Raven makes very powerful jets of fire that supposedly home in on enemies. Have a guess at its name.
Despite being called "balefire," it is not actually fire of any kind except metaphorically, as it "burns the threads from the Pattern. " It appears as a white beam that more or less instantly annihilates what it's aimed at.
The Banned and the Banished also uses the term "balefire" for fire from evil magic. It has many properties of normal fire, but it freezes instead of burns. (Good spellcasters can also create fire, but once started it functions like normal fire.)
The destructive, rare and difficult to control white fire from The Chronicles of Thomas Covenant. Curiously, "Hellfire!" is one of Thomas Covenant's favorite sayings.
In Dungeons & Dragons, it's manufactured by Devils and can burn creatures made of fire. Ever watch a fire elemental burn to death? Not pretty Absolutely awesome. (Some sources say that it's "not truly fire" at all" but an evil form of energy unique to Hell.) Particularly useful since about half the monsters in the game are resistant to normal fire to some extent.
Adapted in a third-party setting called "Infernum". There, it's basically negative spiritual energy (despair, pain, misery) given physical expression as sickly green-black flames, which are capable of consuming flesh, bone and soul with equal ease and which thus makes it especially powerful against creatures like demons and angels. It consequently has its own damage type (and damage resistance), so ordinary Fire resistance is worthless against it (although, conversely, a character with only Hellfire Resistance is defenseless against Fire damage).
For a less evil version, the Searing Spell feat from Sandstorm can make your normal fire spells burn hot enough to deal partial damage even to creatures immune to fire.
The cleric spell flame strike has shades of this, attacking with a 50-50 mix of fire and divine energy. The fire can be resisted, but the other half can't.
The first edition of D&D had The Phoenix radiate this. To get a resistance to this fire, you needed one of the feathers dropped by said Phoenix as a spell component.
Third edition has Mephistopheles, the Lord of Hellfire, who grants warlock followers the power to draw upon his powers of hellfire that function as normal fire damage, except that effects that provide resistance or immunity to fire damage don't affect them. He claims to have discovered Hellfire; whether this is true or not, he is, no doubt, better at using it than any other devil, and has created many horrible devices associated with it, such as Hellfire Engines.
Hellfire Warlocks are a type of mortal wizard who can harness this form of energy, mentioned in the 3.5 Edition. (Not all of them are evil, but most are.)
The Book of Exalted Deeds supplement also has a spell which creates "heavenlightning" that functions in the same way.
Warpfire in Warhammer and Warhammer 40,000 is evil fire drawn from the Warp. Unsurprisingly, it's chiefly the weapon of daemons, their servants, and the odd race of evil rat-men (who have Warpfire flamethrowers). Tzeentch's daemons in particular are little more than living flamethrowers, and vehicles dedicated to Tzeentch in 40k are covered in eldritch fire. There's also the Holocaust power, which is incredibly dangerous and deadly, and burns Demons just as well as anything. Bonus; it makes resurrection impossible and even kills immortal demons.
Mutants & Masterminds classifies Hellfire as a type of magical energy that looks like fire but isn't. It can be any color, most elements, and act as numerous other powers.
In an interesting variation, infernal powers in Exalted tend to use the burning, poisonous light of Ligier, the demonic Green Sun of Malfeas, in the same manner as characters in other settings use hellfire. In addition to the usual attributes of a Hellfire-analogue, this can also infect victims with Green Sun Wasting, a truly horrifying supernatural disease that makes Ebola look like the common cold in comparison.
The fandom often jokes that Ligier's fire is basically radioactive, which technically makes the Green Sun a more "realistic" sun than the Daystar.
Essential Flame in GURPS: Magic is similar in concept to this but seems to be based more on Plato than Christianity.
In the Exile/Avernum series, quickfire is an artificial, very powerful magic flame that ignites even thin air to create a wall of flames that spreads as fast as a man can run. Nothing short of cold rock or very powerful magic can stop its spread.
Hellfire is a damage type in the roguelike game To ME. Unlike normal fire, it cannot be resisted and evil creatures take double damage. The game also has holy fire.
Similarly, the Roguelike crawl has a damage type hellfire - some monsters resist it, players can't (contrary to almost all other types of damage). Hellfire attacks are always ranged area effects. They're most commonly used by various demonic monsters at the high end of the power scale, but can also be invoked by player characters with a specific mutation or wielding one of a very small set of artifacts.
World of Warcraft has this as a - surprise! - warlock spell, which spews apparently unholy flame in a radius around the warlock, dealing decent damage per second in an aoe but also injures the warlock. Oddly enough, the self-damaging part is the thing warlocks use it for as they have more powerful AoE but dying to hellfire doesn't cause durability loss.
Chaos Bolt, another warlock spell, is probably a better example. It fires a bolt of chaotic fire that goes right through absorption effects and ignores fire resistance. It does not, however, work against targets that are completely immune to fire damage.
Also, NPC demons tend to use green fire, leading to some running jokes about giving warlocks green fire.
They did give warlock's green fire. There is a long quest chain that allows a Warlock to turn all his spells that use fire into green fire.
WotLK also introduced the concept of dual-element spells, primarily so you can't easily resist them by stacking a specific magic resistance (usually fire). Spellfire, Spellfrost, Frostfire, etc.
Castlevania's Dracula has a three-to-five-directional fireball attack by this name. On occasion, he cranks up the damage factor and throws big black METEOR-fireballs at you.
Alucard can mimic the three-fireball and two-meteor-fireball attacks EXACTLY in Castlevania: Symphony of the Night. It is so immensely satisfying to be able to pull Dracula's shenanigans on his henchtwits. To gamers unfamiliar with the old Nintendo Hard console titles and their relatively slow Belmont heroes, the fireballs may seem like small potatoes, but even very skilled, hardcore gamers have been reduced to incoherent howling by the original Castlevania I and the Sharp X68000 remake of that title. (We do not mention Castlevania III: Dracula's Curse around these gamers. They will go insane.)
Soma Cruz, can also perform the three-fireball attack if he equips the right soul. In Castlevania: Aria of Sorrow, it's one of the three souls he needs to equip during the battle with the Disc One Final Boss to unlock the path to the true ending.
Pokémon: Throughout the series, various Pokemon have attacks that are much like hellfire, one example is Ho-Oh's Sacred Fire.
A more serious version is Shadow Fire from XD. Exclusive to Moltres, it's a Shadow-empowered Flamethrower attack that will barbecue even the sturdiest Water, Rock, and Dragon Pokemon. Then again, Shadow power is super-effective against everything other than itself...
Black and White also gives us the inaccurate but powerful Inferno, which will always leave a burn. To further the resemblance, it's actually called Purgatory in Japan.
The Gold Pokedex entry for Houndoom is meant to evoke this trope; apparently, the pain inflicted from the flames it breathes will never go away.
Hellfire is also the fire elemental Spirit attack in Baten Kaitos: Eternal Wings and the Lost Ocean.
City of Heroes soon-to-be-released Demon Summoning powerset for Masterminds has a few demons that attack with hellfire, as well as giving the Mastermind a whip made of it. While regular fire attacks have the secondary effect of igniting enemies for additional fire-type damage over time, hellfire's damage over time is toxic-type, and applies a damage resistance debuff to its targets.
Scorpion of Mortal Kombat fame has power over hellfire as a side effect of being undead. He pretty much only uses it to kill people by breathing it on them.
One of his special moves from Deadly Alliance onward lets him summon flames from the ground.
The titular character of the webcomic Zebra Girl has the ability to summon hellfire which makes anyone she's mad at spontaneously combust. In a subversion, Epileptic Tree wisdom states that the burns made are skin deep, so that the victim can be fried again...and again...and again.
Dragon Cave has a species called "Hellfire Wyverns". The submissive males are the bright fiery red usually associated with this trope, while the more violent females are the bright blue of hotter flames.
Thermite is a reaction between a metal and a metal salt (typically iron oxide and aluminum). The reaction generates temperatures of approximately 2500 °C and releases molten iron. Its also self-oxidizing so good luck putting it out. World War II soldiers used it to melt Jeep engines and artillery cannons.
By comparison, a candle burns at 1000°C, a blowtorch at 1300°C and an oxygen/hydrogen flame (aka a rocket engine) at 2000°C. (The numbers depend on certain assumptions about local environmental conditions, otherwise blast furnaces wouldn't work, but the point stands - thermite is hot.)
Thermite was also used by artillery: it burns through thin sheets effortlessly and small burning pieces typically dispensed with a shell or rocket has just enough speed to get embedded in the wood. Soviet Army in WWII has thermite ammo for cannons, MLRS... everything, though dropped it because this was devastating against large flammable things, but useless against tanks or infantry—unlike a sticky liquid incendiary.
Industrial electric arcs invoke this trope, from arc welding (no not that type) to electric arc steelmaking. Arc steelmaking is where humans effectively use man-made lightning to melt steel and rock at temperatures hotter than a volcano, with the arc furnaces drawing as much power (or more) as a 747 at takeoff - or a small town. Nucor's Crawfordsville, Indiana plant, at full bore, needs a quarter of a typical nuclear power plant's output. Electric arc furnaces sound like a Gatling gun at artillery calibers. Arc temperatures average about 6000°C - steel melts at 1525ºC.
Chlorinetrifluoride. So horribly dangerous and impossible to control that the Nazi leadership, which experimented with this substance as a combination of flamethrower fuel and poison gas, ruled it too dangerous and not worth the potential risks. Colorless, poisonous, a stronger oxidizer than oxygen, a stronger fluorinator than fluorine gas and hypergolic (i.e., it starts making things burn immediately on contact) with nearly anything, it will cause things to burn that absolutely should not be flammable - things like ashes, bricks, water, sand, test engineers, and asbestos. If you try to dump sand on Chlorine Trifluoride in order to put it out, it will instead merrily proceed to burn the sand (and then the ground beneath the sand). The closest thing to actual hellfire the real world has to offer.
The major product of most chlorine trifluoride reactions is hydrogen fluoride, a very corrosive acid that is extremely toxic beyond even beyond its acidity. Spilling a bit on a few centimeters of skin can easily destroy the bones underneathnote It's not burning it down to the bone, it's going through your skin first, as well as any nearby nerves faster than they can transmit the pain of the acid corroding your skin. Also, it can deplete your blood of serum calcium and give you a heart attack. Hellfire indeed.
In many ways, chlorine trifloride is the gentler cousin of DioxygenDifluoride. This quote sums it up nicely:
When 0.2 (mL) of liquid dioxygen difluoride was added to 0.5 (mL) of liquid methane at 90 K (-183ºC), a violent explosion occurred.
And, and before you get any funny ideas, yes. The crazy bastard that did said experiment also applied Dioxygen Difloride with the above Chlorine Trifloride, something the writer for the article could only respond with "say what?"
So we're clear, this is a substance with the capacity to release the energy equivalent of a hearty breakfast if you get a couple of molecules of it together and breathe hard in the same room; the only record of any serious experiments attempted with it was by a single scientist in the sixties, who soon concluded it was too dangerous to study.
The parade of chemical flames:
Acetylene/oxygen flame, a most common and widely used in industry. 3300 °C, 6000 °F. Melts most materials in your house.
Atomic hydrogen flame. No need for oxygen. Atomic hydrogen is produced by electric discharge and 'stable' in gas form (fuses into molecules slowly). When directed onto a hard surface, it is catalytically fused back into molecules and produces up to 4000 °C. Enough to melt tungsten, but not enough to melt special ceramics, which require about 4500 °C to melt.
Cyanogen/oxygen flame - 4525 °C (8180 °F). Cyanogen is toxic, but not uncommon in chemistry, so the flame can be produced by any reasonably determined person.
Dicyanoacetylene/oxygen flame: 4990 °C (9010 °F). Our sun is about 6000 °С on its surface and most common kind of stars — red dwarfs - are cooler — about 3000 °С.
Of course, in terms of raw energy, it's hard to beat nuclear fusion. It is what stars run on, after all.
It's astonishing how little power is produced by each cubic meter at the center of the sun.
However, there are things that beat it easy. So known gamma-ray bursts are produced when big amounts of matter rush into a black hole at a great rate. The estimated temperature is about 1-10 * 10^9 Kelvin.
Actually its amazingly easy to beat mere conventional nuclear fusion. Muon-aided fusion, energy release from matter falling onto degenerate stars (white dwarfs, neutron stars, other more exotic kinds), antimatter annihilation, theoretically the temperatures of evaporating singularities reach really ridiculous levels too.
High Test Hydrogen Peroxide. When it disassociates at 100% purity you have a roughly 1270 °C cloud of steam and oxygen which can be used as rocket fuel all by itself. The disassociation result wants to hypergolicly set fire to anything it can heat up to it's autoignition temperature.