Monkey D. Luffy is the main character of One Piece. He is one of the most well-known characters within the anime community. He appears to be a simple-minded character, but he knows when to be serious. Luffy had really big dreams ever since he was a kid and in order to fulfill these dreams he needed to become powerful.
Luffy possesses the Gomu Gomu no Mi, which made his entire body rubbery. He has developed several gears that have allowed him to enhance his power. Also, Luffy is able to look a few seconds into the future with his Observation Haki and with Armament Haki he can protect himself. Since Luffy is a very powerful character, we will be taking a look at five characters that he can't defeat and five he can.
10 Can Defeat: Sakata Gintoki
Sakata Gintoki from Gintama is the first character on the list. He is akin to Luffy in terms of personality. He cares deeply about his friends and he is willing to go to any lengths to protect his friends from any harm.
Gintoki is a master swordsman and his skills with the sword are only matched by just a handful of characters. However, Luffy's power is far greater than Gintoki's and if they have a 1v1 fight, it will end in an easy win for Luffy.
9 Can't Defeat: Naruto Uzumaki
Naruto is a member of the "Big 3," like Luffy. He is the protagonist of Masashi Kishimoto's manga of the same name. As a kid, Naruto dreamt of becoming the Hokage of his village, but more importantly, he was concerned with earning the acknowledgment of the people.
Naruto trained hard and succeeded in becoming the strongest ninja in history. Naruto is capable of blowing up planets and his attacks are much stronger than what Luffy has to offer.
8 Can Defeat: Joseph Joestar
Joseph Joestar is one of the most adored characters within the JoJo fandom. He is not the bravest person in the world, but he steps up when the need is a must. Joseph learned to use Hamon from his mother Lisa Lisa. He was able to keep up with the rigorous training that she put in front of him.
Later, he awakened his stand after DIO came back to life. Joseph's biggest asset is his wit, which allows him to outsmart the smartest of characters. He may be able to dodge a few attacks, but he won't be able to land any hit on Luffy due to his Observation Haki.
7 Can't Defeat: Son Goku
It would not be an exaggeration to say that Son Goku is the most famous anime character in existence. Dragon Ball universe is filled with super-strong characters that are capable of wiping out entire galaxies. Goku is one of the strongest characters not just in Dragon Ball, but within the entire anime world.
Luffy's biggest mistake would be to get on the wrong side of Goku. There isn't any competition and even if Luffy got over a hundred attempts to beat Goku, he would still be unsuccessful.
6 Can Defeat: Boruto Uzumaki
Boruto Uzumaki is the son of the legendary ninja, Naruto Uzumaki. He leads a new generation of ninjas. Boruto is a fledgling, but he's still a talented ninja nonetheless. He is dubbed a prodigy by his peers and teachers, and he has shown what he's capable of achieving already.
Boruto has a lot of weapons in his arsenal, but none so powerful that it can seriously damage Luffy.
5 Can't Defeat: All Might
The former Number One hero is next on the list. As a pro-hero, All Might has faced countless strong opponents, which helped him to grow as a person and as a hero. All Might's quirk is called One for All. It is one of the strongest quirks in the series and it was almost impossible for most villains to get the better of All Might in a fight.
The quirk grants him insane speed and strength, which makes a nemesis for his opponents. In his prime, All Might would decimate Luffy very easily.
4 Can Defeat: Thorfinn
Thorfinn is the son of one of the greatest Viking warriors. He held himself responsible for his father's death and so he only thought of killing Askeladd. Thorfinn was exposed to the harsh reality of war. He killed numerous people on the battleground and slowly he matured into a strong fighter.
Thorfinn relies on his speed instead of sheer strength and it managed him to fight a person as strong as Thorkell. However, Luffy is much more powerful than an average human and he can easily defeat Thorfinn.
3 Can't Defeat: Meliodas
Meliodas is the leader of the Seven Deadly Sins. He is without a doubt the strongest member of the group. Meliodas' unique abilities make him a formidable opponent. His Full Counter can deflect any incoming physical attack with twice the power back at the opponent.
His full power is pretty frightening and he can prove to be a difficult test to overcome. Luffy is not capable of beating a character with so much power.
2 Can Defeat: Tanjiro
Tanjiro is the main character of Demon Slayer. His entire life changed after Muzan attacked his family. Only his sister, Nezuko, survived the attack. After a brief scuffle with Giyuu, he went to train and become a Demon Slayer. He was willing to go to any length to convert his sister back into a human.
Tanjiro learned several techniques from his teacher and that allowed him to beat very strong enemies. But, Luffy is just a cut above anything Tanjiro has faced and it will be a one-sided match.
1 Can't Defeat: Toriko
The final character on the list is Toriko. Toriko is one of the four Gourmet Kings. He is insanely powerful. Toriko's strength allows him to fight humongous monsters with relative ease. Toriko's punches are very dangerous and taking one head-on is a very bad idea.
He also possesses great durability so he can withstand a lot of strong attacks. A fight between the two will be really interesting, but Toriko will very likely win this fight.