BM's skin is impenetrable since birth. She is genetically natural born destroyer etc. Is this an outlier?
Imo Luffy is an outlier but only slightly. In my opinion, Luffy has extreme affinity in learning. He is so creative in finding the solution in combat, or at least Oda depicts him as such. Combine this with extreme willpower when the stakes are at play, and you get someone who will not stop evolving combat-wise.
Imo there is no one with this extent of learning ability in OP world. Maybe in that way, Luffy is an outlier. But that is the blessing of the MC. Moreover, Oda compensates by making Luffy constantly making mistakes during his battles and adventure. Being reckless, being boyish and childish, prone to ambush etc. Oda also make ladder steps to accomplish his power progression.
Doflamingo - Cracker - Enraged Army - Katakuri - Kaidou. Luffy has learning talent, picking things up from the enemy or surroundings and incorporate them into his own abilities, so you can see each fight as a life-and-death learning session for Luffy. By this, he builts himself up slowly but surely, becoming stronger and stronger.
If many other fighters get extremely powerful devil fruits and weapons from the get go (LIGHT AND GRAVITY DEVIL FRUIT ARE YOU KIDDING ME) other fighters get indestructible bodies from the start. Luffy catches up by learning everything he can. This is his boost.
But, Oda's portrayal of this is almost instantaneous since imo he lacks ability to portray Luffy's building up his thinking process, internal monologues, makes us feel Luffy's trial and error phases, and character progression depiction within the learning process (combat). Oda also chose to keep Luffy's brattish and reckless traits instead of a grown-up boy filled with wisdom from his experience. He still made mistakes everywhere and makes a fool outta himself and Oda chose to retain this trait completely, no strategizing or being creative when plot restrict him from it.
These two things resulted in "instant" vibes at each decisive combat moment. Imo Oda dont have the ability to depict the learning process properly, this is why Luffy's growth is often perceived as an asspull, even though Luffy had met bits and pieces he completed the puzzle of combat learning from. But boy if Oda learn this storytelling method, itll be glorious to portray char development. A manga with extremely good example of learning process is Vagabond. That is one masterpiece mofo of storytelling.
So on topic yeah imo Luffy is an outlier. But only slightly, and he is a somewhat realistic outlier, there are phases and methods to his progression even though he is still goofing around, a character trait which should change or mature sufficiently by now imo. And dont worry Oda makes everyone relevant into outliers by him wanting to hype everyone.
