Tropes A to B (Adaptation-Induced Plot Hole, Arc Villain, Berserk Button, Beware the Silly Ones, Big Brother Instinct, Bowdlerise, Break the Cutie) | Tropes C to D (Call-Back, Chekhov's Gun, Cliffhanger, Combat Pragmatist, Crouching Moron, Hidden Badass, Curb-Stomp Battle, Dark and Troubled Past, Deconstructed Character Archetype) | Tropes E to F (Early Installment Weirdness, Famous Last Words, Foreshadowing) | Tropes G to J (Heart is an Awesome Power, Hypocrite) | Tropes K to M (Laser-Guided Karma, Logical Weakness, Mass "Oh, Crap!", Moral Myopia, Muscles Are Meaningless) | Tropes N to P (Nice Job Fixing It, Villain, Oh, Crap!, O.O.C. Is Serious Business) | Tropes Q to S (The Reveal, Shout-Out, Spanner in the Works, Superpower Lottery) | Tropes T to Z (Wham Episode, Wham Line)
The Devil Fruits as well as specific other powers of One Piece can frequently fall into Logical Weakness.
- Luffy's rubber body, which makes him more or less immune to blunt force, renders him no less vulnerable to blades than he ever was. For Luffy, heat also apparently makes him extra squishy. He also requires constant muscle control to not stretch.
- Nico Robin's ability to grow countless copies of her body parts from any solid surface within a large radius, including right from the bodies of her enemies, and perfectly control them as if they were normal parts of her body, would be incredibly powerful if not for the fact that copies also transfer feedback as they were normal parts of her body — not only does she feel pain whenever they are damaged (which happens easily, given that they retain her unimpressive durability), enemies can channel harmful Devil Fruit effects through them.
- Several Alabastan soldiers drink a potion that makes them extremely powerful, but will kill them in minutes. Crocodile responds by simply waiting through the duration, out of reach of their attacks, letting these soldiers die with them unable to do anything in response.
- Crocodile is finally defeated when Luffy figures out that Crocodile's ability to turn into sand can be hampered by becoming wet, so Luffy coats his hands with his own blood, allowing his punches to work.
- One of Enel's top fighters, Satori, has the same ability to predict any attack. However, Satori relies on it so much that when something unexpected happens, he gets really rattled. Luffy takes advantage of the distraction to wrap Satori up with Luffy using his rubber limbs in a grapple. Satori can see Sanji's ensuing kick coming, but bound as he is, Satori has no ability to counter it. Just because Satori knows an attack is coming doesn't mean he has the ability to avoid it automatically.
- God Enel's lightning-based powers have no effect on rubber, thus allowing Luffy to harm him. But even then, Enel has Observation Haki that allows him to predict any attack, so Luffy still can't hit him. Luffy gets around this by ricocheting his punches off of a wall. Since Luffy isn't consciously controlling where his attacks are going after they've ricocheted, Enel can't predict them, and he gets pummelled by the repelled punches. Enel eventually loses to an attack that he can foresee but not stop until too late because it's simply too fast; just because he knows something is coming doesn't automatically mean he can react fast enough to stop it.
- Logia in general fall into this category, as they are literally elemental beings (though not always stuff we'd consider "elements"), and as such are vulnerable to the weaknesses of that element. Lightning losing to rubber, sand losing to liquids making it stick together, etc. Considering how powerful a Logia is, and how invulnerable they are, exploiting a logical elemental weakness is one of the few things on the entire planet that can even potentially harm them, unless a person has Armament Haki, which lets them hurt Logia users even if they're in an elemental form. Plus there's the matter that Logia are more sensitive to water than other Devil Fruit users: as in Luffy can get splashed and still fight (even if he's submerged, he just can't move himself, though others can still manipulate his body), while if someone like Smoker gets doused, he can't transform the wet body part until it's dry.
- Blackbeard's Dark-Dark Fruit, despite being a Logia, works very differently. His element is darkness, which has black hole-ish properties... but said gravity is constantly applied to him. It not only forces his own body to stay together (he can't assume an elemental form), but it also attracts enemy attacks towards him; this makes said attacks harder to avoid, stronger and more painful.
- Franky became a cyborg after suffering severe injury, giving him numerous gadgets and a super-durable steel body. However, since this was achieved by operating on himself, his back is unprotected — he can't modify something if he can't see or reach it.
- The Iron Body defensive martial art used by elite World Government agents works by flexing one's muscles so much that they becoming hard as iron, preventing injury. Naturally, this does nothing to prevent them from feeling heat or cold. The CP9 at Enies Lobby are as threatened by the Buster Call as everyone else, as the explosions from the bombardment will still hurt and kill them and Jabura is defeated after Sanji uses his new burning hot Diable Jambe kicks on him, specifically saying his Iron Body didn't prevent the heat from scorching him at all.
- Kalifa's Soap-Soap powers may De-power any skilled fighter, but she would immediately be vulnerable if someone washes the soap away with lots of water.
- Perona has the power to generate ghosts that strip anyone's spirit and optimism from them. But to her shock, they don't work on Usopp. He's such a pessimist he actually inverts the power: depressing the ghosts and even Perona herself.
- Magma beats fire due to the hotter temperatures and magma being able to snuff out fire from its oxygen source. Meanwhile, ice has a hard time against fire and to a greater extent, magma. For an odd example, the more or less completely useless by this point, Mr. 3's wax power, in fact blocks almost every single poison Magellan has, although it's almost completely useless in the intensely hot fourth level of the prison.
- Sugar with her Hobby-Hobby Fruit has two:
- She can Un-person anyone out if she is able to touch them. People fast enough for her are able to avoid her, and as it is a consciously maintained ability, if someone manages to knock her out, her fruit's powers will be undone immediately.
- Her ability to Un-person people affect everyone, herself and her allies included. After ten years of transforming dissenters into toys, they are completely unprepared when the toys are brought back to humanity and revolt, because they couldn't remember who or how many they transformed.
- Pica's Stone-Stone Fruit initially seems like an utter Story-Breaker Power. It allows him to assimilate with and control stone, and everything on Dressrosa is made of stone. He's finally beaten when Zoro realizes that if you cut his stone form in half, he has to escape into one part of it, and so Zoro repeatedly halves his giant stone form while keeping the parts in the air, until there isn't any stone large enough for Pica to hide in, nor can he escape into the ground. It's over for Pica after that. (Such an opponent needs to be strong enough to cut stone in the first place, of course.)
- This logical weaknesses was actually attached all the way back to Buggy the Clown. While his Chop-Chop powers enable him to split his body into numerous floating pieces, some part of his body needs to be the "base" part and stay on the ground. That's why Luffy is able to find and successfully attack his feet.
- Charlotte Cracker of the Big Mom Pirates ate the Bisc-Bisc Fruit, which gives him the power to conjure up biscuits. Since Heart Is an Awesome Power, he's skilled enough to reshape the biscuits into armor and warriors that Luffy needs his Dangerous Forbidden Technique to fight against. Luckily, our Idiot Hero figures out a Mundane Utility; since biscuits are edible, all Luffy needs to do is eat Cracker's creations to hold his ground (though due to Cracker's abilities and Haki, Nami had to use water to soften them up at first, like regular biscuits.)
- Trafalgar Law can swap the positions of anything and rearrange parts of whatever is within his sphere of effect, which he triggers by doing a "come at me" gesture with his right hand. Vergo is able to get the best of Law by closing in faster than Law can complete the gesture.
- A villain in a Filler arc has the Pet-Pet Fruit, which creates Hypno Trinkets that make anyone affected by them have to obey his orders. Trafalgar Law defeats this by putting in ear plugs, since someone who can't hear the orders, logically, can't obey them.
- This is also Scratchman Apoo's weakness, having a Devil Fruit power that translates music and sounds he makes into attacks. If one is outside the hearing range of the noises Apoo is making, or even if they just cover their ears, the attacks have no effect. Of course, that brings up a logical weakness of its own... "WHAT?!"
- Perospero's Lick Lick Fruit lets him generate an endless amount of candy syrup which he uses to make everything from escalators to prosthetics to iron maidens. Being syrup, it's vulnerable to heat which will melt it.
- Katakuri's Mochi Mochi Fruit is ridiculously powerful but weak against most liquids, which will remove its stickiness. At one point, Jinbe counters it with black tea. Much like Cracker's Bisc-Bisc Fruit, the mochi is also edible.
- Katakuri also displays another Logical Weakness to Observation Haki, despite being a master. If the user's concentration and resolve is broken by any means, for instance showing great uncontrolled emotions, they can't use it for a while.
- Shigan deals immense damage with a single poke but, due to the fragility of human fingers, if someone manages to block it, the user will likely break their fingers. Jinbe cripples Who's-Who's ability to fight by breaking his index fingers this way.
- Kid's power hinges on using surrounding metal constructs for his attacks, which is why he spends a lot of time on Onigashima running around collecting various weapons on his way to fight Kaido.
- Similarly, if his Damned Punk cannon is disrupted at short-range, the resulting dissipation of the surrounding metal with the charge causes the attack to blow back on him.
- Hawkins' voodoo-inspired power transfer any damage he gets to his target on the exact same part of the body. He gets attacked in the chest, his target gets a wound in the chest. A problem arises when he's fighting Killer while Hawkins is targeting Killer's captain, Kid. Killer attacks Hawkins' right arm, but because Kidd doesn't HAVE a right arm (he lost it in a previous battle), there is no target for the damage to go, and Hawkins takes all the damage.
- Zigzagged with Admiral Ryokugyu's Woods-Woods Fruit, which lets him turn into a living forest. Raizo attempts to hit the admiral with a fire blast, but Ryokugoku reveals that he's already figured out how to defend against such an obvious weakness and shrugs off the attack. Then Momonosuke shooting out dragon fire, which does hurt Ryokugyu. It's unclear if it's the type of fire, or just the force of the firestream that's doing damage, however, given that Momonosuke's artificial Devil Fruit was based on Kaido's.
- Doc Q's new Sick-Sick Fruit allows him to infect other people with various diseases. However, just like many diseases, It Only Works Once: anyone who manages to overcome a specific disease will become immune to it. Moreover, since these diseases are created from a Devil Fruit power, they can be nullified by a high amount of Haki.
- Admiral Kizaru's Glint-Glint fruit is one of the most powerful in the series, particularly because he moves at literal light-speed once he engages it, and can move across islands in an instant, let alone within a battlefield. The windup is not instantaneous, however, and since light cannot actually curve by itself he can only move in straight lines until he disengages. A fighter with good enough Observation Haki can know he's coming and give him the slip. Kizaru also thinks and reacts at a normal human speed, not light-speed, so if he makes a mistake or an error of judgment, it can sometimes take him a while to figure out what just happened due to his extreme speed of movement.
- Jewelry Bonney has two:
- Her "Distorted Future" ability, involving turning her or others into a possible "what could be" future variation of them, is fueled by her believing it could be possible. As such, she is extremely vulnerable to Break Them by Talking and very reliant on her own self-confidence. Right as Saint Saturn is about to kill her, it becomes extremely weak as she's reaching the Despair Event Horizon. It's also implied that the reason it is such a powerful move in the first place is because she's actually a twelve-year-old with the imagination to match, and her ability will become weaker as she grows older and more certain of what is and isn't possible.
- Her ability to change the age of things, both alive and not, doesn't work on The Ageless.
