Immunity Attrition

The Flash: I thought you couldn't read their minds?
Martian Manhunter: I'll just have to try... harder.

— Justice League, "Starcrossed"

Some characters can shrug off whatever their opponent throws at them. Except that doesn't stop their opponent from continuing to try. And wouldn't you know? The more the opponent keeps lashing out, the less effective the character's defense against it becomes, until eventually they go down as easily as anyone else. Looks like their immunity only lasted in the short run, but prolonged exposure still rendered them vulnerable. They're Not So Invincible After All!

Supertrope to Dented Iron, where the damage a Made of Iron character takes starts to take its toll over the years, and Untouchable Until Tagged, when a single bruise/crack/etc. in your immunity makes you easier to be beaten down. Compare and contrast Scissors Cuts Rock. See also Scratch Damage and Tim Taylor Technology.

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Examples:

Anime and Manga

• Fullmetal Alchemist: Homunculi can heal any damage so long as the Stone that is their core remains intact... but they only have a finite amount of energy to do so. It's a large amount of energy — enough to replace their entire body more than once — but not unlimited. They can be killed simply by forcing them to take lethal amounts of damage over and over and over again.
• My Hero Academia:
  • When the League of Villains storms the school, they unleash a Nomu (a genetically-engineered creature with multiple Quirks) designed to counter All Might by being heavily shock-absorbent. However, All Might deduces that there must be a limit to how much the Nomu can absorb, and just keeps punching faster and harder until he finally goes beyond said limit.
  • Tetsutetsu Tetsutetsu can turn his body into steel thick enough to block bullets. However, when he uses this to defend against Mustard's gun, Mustard just keeps shooting the same place over and over again, cracking the steel.
• Played for laughs in One Piece with regards to Magellan: His Devil Fruit makes him mostly immune to poison, and eating it is how he produces the poison he himself releases. Unfortunately, he has to (or chooses to) eat so damn much that it gives him chronic diarrhea.
• Pokémon: The Original Series: In the episode "Fire and Ice", during the battle between Ash's Kingler and Pete's Cloyster, Cloyster closes his shell, rendering Kingler's punches ineffective. Ash, however, orders Kingler to keep hitting Cloyster, and sure enough, after enough hits, it becomes too much for Cloyster and his shell cracks open.
• In Saint Seiya: Poseidon Saga, the first Mariner Seiya has to fight is Hippocampus Baian, a Barrier Warrior that can deflect Seiya's attacks with wind barriers. Very confident in his powers, he can't believe that his barriers are finally broken by Seiya after many attempts, being soon defeated just as Seiya did in the past against Silver Saint Misty, who had a similar fighting style.
• One chapter of Sleepy Princess in the Demon Castle has Syalis inadvertently wearing an artifact that makes her immune to status effects — including sleep. She continually exposes herself to status effects, trying to force herself into sleep, until finally the artifact breaks. Unfortunately, she's sleeping on a massive poisonous mushroom at the time...
• Sonic X: In episode 73, Shadow storms through the heroes' spaceship to pursue Cosmo, handily disposing of any of their attempts to stop him. After a tense fight with Knuckles however, he stands the winner... only to faint in turn, finally succumbing to exhaustion. It's revealed he even had to take off his energy rings to finish Knuckles before he gets back up and continues unfettered. Interestingly the English edit omits this scene entirely, making Shadow seem genuinely unstoppable.

Comic Books

• During the events of the Angel & Faith series, Angel calls Spike in to help him deal with Eyghon the Sleepwalker, reasoning that while Eyghon can possess the unconscious or dead, their status as vampires with souls would make them immune, since Angel did defeat Eyghon way back in "The Dark Age" in that manner. However, they're proven wrong; Eyghon has regained his true form and power, and successfully possesses Spike.
• DC Comics:
  • In the second volume of the Batman Vampire Elseworlds trilogy, Bloodstorm, the now-vampiric Batman is revealed to be immune to crosses and holy water, since he's abstained from drinking human blood, which works to his advantage when Joker lures him into a church filled with crosses as part of a Death Trap. However, Batman soon succumbs to his bloodlust and sucks the Joker dry, losing his immunity.
  • Final Crisis: In The Flash tie-in "Rogues Revenge", after declining Libra's offer to join his army, he created his own version of the Rogues, who eventually battle the original ones without success. The most notable case in which this trope applies is Heat Wave against Burn, Libra's counterpart, which is also a pyromaniac, just like him. When the two fire their weapons at each other, Heat Wave barely sweats and notices to Burn his weapon isn't powerful enough and his suit also of poor quality. It ends with Burn burning to the death.
  • In the Superman comics, Kryptonite is highly lethal to Kryptonians, but has no immediate effect on humans. Thus, they can easily handle it without consequences. However, it is still a radioactive material so prolonged exposure to Kryptonite will eventually cause aggressive forms of cancer in humans. Lex Luthor discovered this the hard way after years of wearing a kryptonite ring as a protection against Superman.

Fan Works

• RWBY: Epic of Remnant: One unnamed White Fang member has armadillo-like armor, and his Semblance can make his skin turn to rock so it can withstand blades. One of the Oprichniki kills him by hammering away at him with an axe until he breaks.

Films

• King Cobra (1999): Hashimoto has Acquired Poison Immunity from snake venom, which lets him survive a bite from the giant snake Seth. However, Seth keeps biting him, which causes him to weaken and die.
• Underworld: Awakening: Quint Lane was modified to be an Uber-Lycan via Eve's blood, making him largely immune to silver. Key word being "largely": Selene takes him out by jamming a silver nitrate grenade into his body just as his wounds heal; when the bomb goes off, the sheer amount of silver released directly into his organs and bloodstream blasts him into Ludicrous Gibs.

Literature

• In The Bartimaeus Trilogy, as a population spends more time around spirits people start being born resistant to their abilities, but it has limits. The character Verroq, usually referred to as the Mercenary, is resilient to such a greater extent than anyone else that he's not just unaffected by magical attacks but absorbs them to grow stronger and tougher. The first time he's defeated, rather than inconvenienced or evaded, is when someone realizes this and deliberately uses no magic to fight him. Regardless he is later killed by a purely magical attack, as extended exposure to the traps guarding the government's most valuable artifacts eventually exhausted his resistance and reduced him to a skeleton.
• Do You Love Your Mom and Her Two-Hit Multi-Target Attacks?: Medhimama uses a spell to make Medhi's classmates fall asleep. Masato isn't affected and explains his armor protects him from status effects. Medhimama simply turns up the power on her spell until it overrides his armor's protection.
• Played for horror in the Night Shift short story "Night Surf": the teenager pack that is the protagonist of the story survived the rampage of a super-virus called "Captain Trips" and, in the face of the fact that the super-flu has a 100% infection and casualty rate, they only assume that they did so because they were immune. The final couple of paragraphs of the story has them discovering that "Captain Trips" has evolved and their immunity, if they ever really had one, is completely useless.
• In Old Virginia by Laird Barron, government scientists are studying the titular old crone who is a servant of an Eldritch Abomination, including having her Mind Control Tested on Humans (with often fatal results) until the scientists develop a mental shield that can protect them. Unfortunately for them, the government task force who are given the job of studying her, decides to do this at a black site, which turns out to be close to the home of the Eldritch Abomination that she worships (it is implied that she might have used her psychic powers to subtly influence the official in charge of the project to choose the place). It turns out that the closer she is to said Abomination, the more her powers increase, so their technology is rendered useless.
• The Tommyknockers: Due to a metal plate in his skull, Jim Gardener is initially unaffected by the alien spaceship, while everyone else around him slowly starts to "become" (mutate into aliens). It also prevents his mind from being read when everyone else gains telepathic powers. But after several weeks of working day in, day out to dig up the ship, and thus being extremely close to the source, Gardener too starts to display the symptoms of "becoming" (like losing his teeth) and realizes it's getting more and more difficult for him to keep the telepaths out of his mind.

Live-Action TV

• Jessica Jones (2015) plays with this trope. Since Jessica grew immune to his mind control powers, Kilgrave eventually tries to invoke this trope by giving himself a power boost in hopes that this will cancel out Jessica's immunity. Unfortunately for him, it fails. Jessica is still immune.
• In Legends of Tomorrow, Nate Heywood/Steel is a Chrome Champion who is Immune to Bullets, but even he has limits. In the episode "Freakshow", he is tied up and repeatedly shot at, which appears to strain him and by the end he's begging for it to be over.
• Star Trek: Voyager: In the episode "Bliss", a telepathic nebula tries to lure the ship into itself so it can eat it. Seven of Nine believes herself to be immune to it because she is a former Borg drone with many cybernetic implants. However, she was only immune to the initial attack because she didn't have the desire to return to Earth that the rest of the crew shared. Once the nebula tried to fool her into thinking something had happened that she did want, i.e., that she had succeeded in escaping it, it turns out that she was as vulnerable as anyone else.

Toys

• BIONICLE: The Pit Mutagen is a powerful substance that can mutate any being exposed to it. However, organic creatures are affected by it so slowly that the effects are unnoticeable, while Brutaka's species have a slight resistance to the point of changing physical appearances slowly.

Video Games

• Batman: Arkham Knight: The Scarecrow has developed a partial immunity to his own fear toxin. Keyword being "partial", as while he can take one dose with no effects, a much larger dosage will cause him to hallucinate his worst fear (a demonic version of Batman) just like everyone else.
• Elden Ring: Crystallians (golems made of pure magic crystal) have incredibly high defense against everything other than strike damage, so trying to hit them with a bladed weapon will just cause it to bounce off of them and leave the player vulnerable to counterattack. However, hitting them enough despite this will eventually cause their crystal bodies to crack, at which point they become extremely weak to virtually all forms of damage.
• Let It Die: Sufficiently-upgraded armor causes rocket launchers to deal scratch damage in the single-digits. Unfortunately for you, any hit will slowly crack your armor, dropping it from near-invincible to partial-resistance until it eventually breaks and leaves you as vulnerable as a regular human. You will learn to fear a clothes iron more than a sniper rifle to the head, simply because of the total number of hits the former causes.
• Star Trek Online: Borg drones will adapt to incoming energy weapons fire after a few hits, but this only reduces incoming damage from that energy type. Even if you don't refrequence your weapons with a cheaply replicateable item, you can still kill the drone with Cherry Tapping.
• Warframe: Much like the Borg example above, the Sentients are able to adapt to whatever damage type they've been hit with most frequently, gaining up to a 95% damage reduction in up to 5 damage types. While Cherry Tapping is possible, it's simply quicker to switch weapons. However, the optimal strategy is to use The Power of the Void, which the Sentients cannot adapt to, and in fact will eliminate all adaptations they've made. Later game options include the Paracesis, the Sentient Slayer which eliminates adaptations and deals bonus damage to them, and the Shedu, a cannon ripped from various pieces of Sentients themselves that can also strip resistances off Sentients.

Web Original

• Codified by StarDestroyer.net. It is always regarded as possible to simply wear down an enemy with sustained fire; to say otherwise is called the "no limits fallacy".

Western Animation

• Justice League:
  • In "Wild Cards", Joker has enough of an Insanity Immunity to Ace's mind-destroying stare that she doesn't affect him accidentally like most people. Once Ace finds out Joker was prepared to betray her, she focuses her power deliberately and entirely on him, rendering him seemingly brain-dead (though he does eventually recover).
  • J'onn cannot read Thanagarians' minds—until the situation is critical enough for him to try harder. Though it proves unpleasant for J'onn himself, it turns out much worse for the other guy.
• Static Shock:
  • Static confronts the Rubberband Man, who is immune to his electrokinetic abilities, and the latter gloats about him apparently being unaware of rubber being an insulator to electrical charges. Static counters that with enough of a charge, even insulators can be overwhelmed. And he proves it...for all of three seconds. He promptly gets stomped on afterwards.
    Static: Let me tell you a little something about electricity. A big enough charge can overload any insulator. (hits Rubberband Man with a huge blast that makes him scream in pain and go flying, but he comes back pissed off) And that one... wasn't big enough.
  • Madelyne Spaulding uses her telepathic abilities to zombi...err, brainwash the entire school after she loses the election to become student council president. Static happens to be immune because his electrical powers produces a kind of Psychic Static (heh). Static gives her a "The Reason You Suck" Speech, and Madelyne tries to bite off more than she can chew by intensifying her psychic assault on him. Unfortunately for her, this only creates a psychic feedback where everyone is turned back to normal, and she herself becomes an amnesiac. She returns in the next season to plague Static though, with another psychic power.
• Star Wars: The Clone Wars: Cad Bane is intelligent and strong-willed enough to be totally immune to a Jedi Mind Trick during an interrogation. So a second Jedi is brought in; Bane resists, but realizes what they’re trying to do and obviously feels pain from doing so. Then a third Jedi joins and Bane starts really feeling it. He still manages to resist, but doing so nearly tears his mind apart, and he tells them what they want to know so they don't do it again.
• Young Justice (2010): Cheshire attacks Aqualad with jellyfish toxin-coated weapons. He says he's "largely immune" to it, but he is slowly weakened with each cut.

Real Life

• The pistol shrimp's method for getting through the durable shells of clams and oysters normally resistant to blunt damage is to simply repeatedly hit them really hard with its claw until they break.

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