Cross-Melting Aura

Dracula helps lighten the cross Van Helsing bears.

For the Occult Detective, The Hunter, and The Men in Black in charge of policing the supernatural threats that step out of line, a thorough knowledge of how Our Monsters Are Different is vital. They need to know all the Weaksauce Weaknesses, the various Kryptonite Factors, and develop Depleted Phlebotinum Shells in order to properly exploit the weaknessess of their prey. This is what helps level the playing field and save the lives of countless heroes as the forces of darkness run from the light hissing and burning.

Except, of course, when it doesn't.

Some especially old, powerful, determined, or twisted creatures may be so completely evil that they actually make the holy item crumble, spontaneously combust or even liquify in apparent fear and impotence. Much like Holy Burns Evil but inverted, the evil character or force defiles the holy / pure item to the point it's destroyed or at least rendered inert.

Of course, such destruction is never subtle and is catered to the holy item. Holy statues will weep tears of blood, prayer slips will have their holy runes drip off, and the Place of Protection will sour and die. And crosses, as seen in the accompanying image, catch flame and burn to ash.

However, the evil character can still be one-upped if the holy influence is combined with a person who has great faith and virtue.

When a person is affected in this way, they are Allergic to Evil. Contrast Turn Undead, which can similarly be rebuked this way by a sufficiently powerful evil entity.

Examples of Cross-Melting Aura include:

Anime and Manga

Meier Link in Vampire Hunter D: Bloodlust causes crosses to bend when he gets near. Not only that, but his presence also causes running water to freeze, mirrors to break, and flowers to wilt and die.
In the animated Hellsing, this is how Alucard defeats Incognito: he uses his cross-melting aura to make a long silver stake to impale Incognito on: first through the chest and heart, then vertically all the way through.

Film

In the Buffy the Vampire Slayer movie, Buffy holds a cross out in an attempt to ward off Lothos and he grabs it, causing the cross to burst into flames. He even mocks her for her "puny faith"... upon which she corrects him by invoking her "keen fashion sense" - and whips out a can of hair spray to turn the cross into an impromptu flame thrower.
In The Devil's Advocate, when Lucifer enters a church he makes the holy water boil by dipping his fingers in and all the angel statuary cry.
In the 1992 film of Bram Stoker's Dracula, Drac's brides make Jonathan Harker's cross liquify off his body as they seduce and drain him. Thankfully the process seems not to have superheated it, as it flowed off his chest harmlessly.
- Obviously, they were gonna feed off him after all. No good if he gets burned alive. Plus it was a small cross, not enough power to ward them off especially if the brides were as powerful as Drac was (the bride that melts it recoils for a bit before regaining her composure and working her magic). Subverted to the vampiric Lucy as she most likely isn't powerful enough to go against crosses (being newly turned an all). But played straight against Dracula who burns the cross Helsing tries to use against him.
In Hellraiser III Hell On Earth, Pinhead liquified the cross held at him by a priest, seriously burning him.
In Van Helsing, Van Helsing holds up a huge honkin' silver crucifix to stop Dracula. He grabs it, screaming in agony; at which point it catches fire, melts, and he laughs.
Lair of the White Worm avoids vampires' weakness to crosses and at one point, the film's antagonist sprays acid-breath onto a crucifix to melt it.
The original Fright Night had scary-movie actor turned vampire hunter, Peter Vincent try and use a cross against the vampire. The vampire takes it away from him and tosses it, noting that since Vincent doesn't believe it will work, it won't.
- The remake has this occur has a crowning moment of snark when Charley tries it on Jerry:

Jerry is cringing and staggering backward from the cross Charley is brandishing at him.
Jerry: No, not the cross, Charley, not the cross...
Jerry grabs the cross as soon as Charley's in reaching distance, invoking the trope
Jerry: No, Charley; not the cross.

Literature

Occurs in The Apocalypse Door by James D. Macdonald.

Wherever the rosary touched the bag above the fungal glop, a thin trickle of grey smoke rose up into the still apartment air.
"Looks like that'll kill it", Simon said.
[...] It wasn't the fungus that was on fire after all. It was the rosary.

In the Eisenhorn book Hereticus, a priest mistakes Cherubael for a manifestation of the God-Emperor and runs to meet it with an Imperial aquila. While the aquila manages to keep Cherubael away at first, eventually the daemonhost manages to melt the aquila.
Justified in 'Salem's Lot. Callahan puts his faith in the cross itself, rather than what the cross represents. Barlow takes it from him and snaps it into bits.
Played with the sun itself by Tolkien. Throughout The Lord of the Rings we've been told that the forces of Sauron like Orcs, Trolls and Nazgul are afraid of the sun, and sunlight weakens or outright destrous them. And in the third book, we see Sauron's army on the march to Minas Tirith. Cue the sun fading and the day becoming dark as night.
Subverted in the third book of The Dresden Files, Grave Peril. When attending a vampire ball, a Red Court vampire (less vulnerable to faith than the undead Black Court) laughs at Michael's cross and grabs it mockingly, saying that it was immune to such things. It then immediately bursts into white flame.

Live Action Television

In the Doctor Who story The Curse of Fenric, the doubting priest's holy symbols are ineffective againts the Haemovores.

Music

The video for Dimmu Borgir's Sacrilegious Scorn has a priest threaten Shagrath with a wooden crucifix. Shagrath merely looks amused, grabs the crucifix, and sets it aflame.

Tabletop RPG

The Baali in the Old World of Darkness. Being satanist vampires, they are the only ones in the setting actually vulnerable to crosses (rather than to faith) but as they grow more powerful, they can repel religious people in turn.
Being the inverse of the Zenith Caste, Midnight Caste Abyssals in Exalted have the ability to toughen themselves against holy beings. This can also, more literally, be a result of Abyssal Resonance eruptions. Lastly, a class of First Circle Demons called teodozjia are basically hardcore Yozi priests, and engage in a battle of this vs. Good Hurts Evil if they come across a Zenith Caste Solar.

Video Games

In the game The Darkness, the final part of the game seems to involve the eponymous Darkness (which is generally weakened by light) supercharging due to a solar eclipse—with the greatest source of its weakness blotted out, it reaches a power level where it explodes lightbulbs that are near it, destroying both light sources and potential light sources.
Occurs in the intro to Castlevania: Dracula X Chronicles.
In World of Warcraft, the suicide/lichification of Ras Frostwhisper by the Lich King is evil enough to corrupt the Stratholme Cathedral, remove its connection to the Holy Light, and consecrate it to the Scourge.