From Saitama's ability to flatten an opponent with a single punch to Majin Buu's knack for turning anyone into candy, anime characters can possess some stranger powers. However, two series have a concentration of the most peculiar talents: My Hero Academia and One Piece.
Devil Fruits grant pirates in One Piece with incredible powers at the expense of their ability to swim. On the other hand, My Hero Academia's Quirks are special powers with which people are born that reshaped society almost overnight. While both are vital to the structure of their fictional worlds, and some are relatively straightforward, there are plenty of weird Quirks and Devil Fruit powers, but which show has the bigger density of bizarre powers?
Normal Abilities
To figure out which series has the larger density of weird powers, it's important to determine which has more "normal" powers. If weird is the outlier, then the series will feel less outlandish. My Hero Academia has a lot of weird powers, but most are pretty straightforward, drawing inspiration from classic superhero characters.
Even Deku's main ability, One For All, is relatively straightforward: superior strength. Uraraka? Reduce and control gravity. Bakugo? Blow up his sweat. These are fairly mundane but effective. Despite that he resembles a rodent, Principal Nezu's Quirk is that he can devise good strategies. It's pretty useful, but not particularly weird.
On the other hand, most of One Piece's powers are abnormal. Sure, Luffy's abilities are similar enough to Marvel's Mister Fantastic, but the way it's applied is strange in a cartoon-physics manner. Luffy's body can enlarge and stretch. That's a relatively normal power, too. It also doesn't help that every Devil Fruit comes with the odd side effect of rendering the consumer incapable of swimming. While there are some oddball Quirks, the average Devil Fruit is a little weirder.
The Strange World of Quirks
What sets Quirks apart from Devil Fruit is that, due to how many Quirks there are in My Hero Academia, a lot of them turn out to be underwhelming. Midoriya's mother, for example, can move small objects. However, some of the weirder powers are far more outlandish.
Characters like Mineta have bizarre abilities: He can rip pieces of his hair out and throw them like gummy grapes at targets. Best Jeanist can control and manipulate fibers, including including the extreme denim outfit he wears, like textile tendrils around him. Sero shoots tape from his arms, while Jiro has sound-input devices dangling from her ears that allow her to listen to remote objects. Shinso can control the minds of those who speak to him.
Even seemingly "normal powers" have strange side abilities. For instance, Tsuyu Asui has frog-like attributes, including a long tongue, but she can also regurgitate her stomach in order to clean it. Fat Gum can absorb impacts into his belly and body fat, which, again, isn't too outlandish. However, he can then convert the energy stored in his fat into raw power, and then burn the fat to increase his muscle mass.
But a lot of the weirdest Quirks are the least flashy. Amajiki can consume the abilities of whatever items he's eaten, which doesn't sound too incredible until he consumes squid and sprouts tentacles. La Brava can tell someone she loves them, causing their power their power to increase -- to the point that a non-combatant like Gentle Criminal can fight on par with Deku. And while Overhaul's ability to deconstruct and reconstruct anything he touches sounds already fearsome, it becomes more frightening when he assimilates other people into himself, becoming a monstrous entity of colossal proportion.
But Devil Fruit Is Weirder
However, as weird as Quirks are, they're always presented in a way in which we can understand their limitations. One of My Hero Academia's strengths is that we see the limits of each Quirk, which grounds them in a sort of reality. On the other hand, One Piece is limited only by the rule of cool: If it's cool, it's allowed.
Sure, some Devil Fruits are fairly straigh0tforward. The incredibly powerful Whitebeard, for example, can create earthquakes -- some of which can upturn tectonic plates. Buggy the Clown can pull himself apart, into pieces, and float them all through the air. These aren't exactly outlandish, but their application can be bizarre.
However, there are also powers like Raiken's Devil Fruit, which allows him to transform into a literal fire god, with multiple fearsome forms worshiped throughout the world. Kaido can become a gigantic dragon. There's also Marco, who can generate healing blue flames and transform into a phoenix. A lot of these powers are odd, but, again, transformations are fairly straightforward.
Then there's Trafalgar, who may have one of the most insane power sets in either One Piece or My Hero Academia, with his ability to create spherical dimensions in which he can manipulate everything. He can use that to teleport, heal or harm people -- or perform any other reality-bending feat he wishes. The laws of physics, in a sense, break when Trafalgar arrives.
Few Devil Fruit powers are as odd as Trafalgar's. However, given how many odd Devil Fruits exist, it's not unreasonable, after comparing the weird extents of both series, to conclude One Piece has the stranger powers. But, ultimately, that's because there are fewer Devil Fruits than Quirks. Devil Fruits are unusual by definition. If they were less weird, they'd be less special. Quirks are supposed to be more mundane. It's no wonder, then, that they're far less weird than Devil Fruit.