Maybe it's the connection the Bible makes between fire and punishment. Maybe it's just that flickering, destructive flames work so well to signify a dangerous, unstable mind. Whatever the case, fire is often used as a motif in fiction for religious fanatics and extremists. It's pretty common to see such a character preaching in front of bonfires or braziers, or, in more extreme cases, burning sacrifices alive.
- Judge Dredd: Judge Fire, one of the Dark Judges, wants to kill everything with fire to rid the world of crime.
- The Hunchback of Notre Dame (Disney): Frollo frequently references the fires of hell (including in his Villain Song, called "Hellfire") and attempts to burn Esmeralda at the stake, as well as burning down a lot of the city. He eventually meets his own death by fire, with a heaping side of Irony, as he says "and he [God] will smite the wicked and plunge them into a fiery pit" before losing his footing on a gargoyle and falling into the "fiery pit" he's made of Paris.
- Billion Dollar Brain: The supporters of General Midwinter are shown burning pictures of Communists in a rally bonfire while he's giving his Motive Rant.
- Clash of the Titans (2010): A rambling preacher burns his own hand in a brazier mid-sermon, showing both his total devotion to the gods and a totally unstable mind.
- The Night of the Hunter: Harry Powell gives his sermons in a small, dark church whose only source of light is a rather large brazier. Although a hypocrite and a thief, his fanatical faith does appear to be genuine.
- Wonder Woman (2017): Invoked by Steve Trevor in an attempt to woo Dr. Maru, by staring at a fireplace and pretending he's a kindred spirit.
Steve: I love fire, don't you? It is like...a living act of entropy. The ultimate weapon of destruction. Reminding us that in the end, everything eventually returns to the ash it came from.
- Anno Dracula: John Jago, an anti-vampire preacher, rants about fire and stakes (two of the only sure means of killing vampires).
- Discworld: In Small Gods, a character from the fundamentalist nation of Omnia shows his God (who's not very attentive) a rather large furnace shaped like a bull, assuring said God that they use it for burning heretical material, not people. Turns out "heretical material" does indeed include people, Omnians just don't consider them thus.
- A Song of Ice and Fire: A subversion: priests of the Red God. The best known one, Melissandre, plays it straight by being a Knight Templar and has quite a penchant for burned offerings. However, other R'hllorists are just ordinary people in spite of the fire motif.
- Supernatural: Angels have a connection to fire: they burn out the eyes of anyone who sees their true form and their basic attack is to sear someone's insides with a touch. However, while they're all unquestionably trusting in God, it's not entirely fair to call them all fanatics.
- Magic: The Gathering: Some beings aligned with Red and White mana tend to mix white's fundamentalism with red's pyromania. Notable examples include the insane angels in Shadows over Innistrad, which have gone on a murderous rampage against humanity and burn everything to the ground.
- Warhammer 40,000: Sisters of Battle, Inquisitors, and other fanatical Imperial organizations traditionally use flamers and other fire-based weaponry. The Order of the Ashen Shrine, a minor Order of the Sisters of Battle, is notable for having an obsession with flames unusual even for the Sororitas, as they believe that it represent's the Emperor's holy word, and for the fire-based miracles that follow them into battle — stories about the order include volcanic fissures opening across battlefields, burning meteors raining upon their enemies, or machines targeted by their forces being consumed in fiery explosions.
- Civilization II has Fanatics, the special unit that can only be recruited by Fundamentalist governments. They're depicted wielding a lit torch.
- Darkest Dungeon: The Fanatic from the Crimson Court DLC is very, very fond of fire indeed. The very first thing he tries to do in every fight against him is to burn one of your heroes at the stake.
- Elden Ring: Fire magic is almost exclusively the purview of faith-based incantations. Even the very few sorceries involving fire require a certain level of faith stat in addition to the intelligence usually associated with sorcery. And unlike holy and lightning incantations, the faiths associated to fire incantations range from morally grey to outright malevolent.