When it comes to destructive power, Saitama can destroy giant spaceships, monsters, mountains, etc. with the bare minimum effort. Bearing in mind Saitama's feats, Luffy's Gear 5th stands absolutely zero chance against him.
With that said, Luffy can still control his environment with Gear Fifth. In conjunction with Future Sight, he could predict Sanji's attacks and bounce him back with rubber. More importantly, Luffy can bypass his exoskeleton with his awakening. he managed to do so against Kaido in One Piece Chapter 1045.
Saitama wins easy. With his ridiculous strength he could simply grab luffy and throw him into orbit, or dunk him in the ocean. or run around him fast enough to deprive luffy of oxygen. there are plenty of passive ways for saitama to kill or incapacitate luffy without haki.
Oh yeah, Gear 5 is now Luffy's most powerful technique and a phenomenon that will make headlines once the anime adapts this arc.
Gomu Gomu no Bajrang Gun
Luffy's Gear 5 allows him to inflate his fist almost to the size of Onigashima and infuse it with Busoshoku and Haoshoku Haki. He then unleashes it at his opponent to land a devastating blow.
It depends on how quick the fight will last. Luffy's Gears are costly and can't be maintained for long stretches of time and neither can Baryon Mode for Naruto. Due to the number of drawbacks the Baryon Mode brings, Luffy will probably clinch victory in Naruto vs. Luffy if they break those modes out.
In addition, Luffy still has his standard weakness to cutting attacks.
While Luffy's Gear Fifth abilities are indeed impressive, they are not equal to Son Goku's mastery. Gear Fifth is an interesting fighting technique that has been used very effectively in combat thus far, but not against super beings like Goku.
Currently, however, Shanks is likely stronger than Luffy, simply due to the fact that the plot demands that of him. Luffy has not surpassed Shanks just yet, otherwise, their future fight would hold no significant value.
Could Luffy beat Goku in Gear Five? No, he can't. The power scaling in both verses is vastly different: one verse has gone from building to moon to planetary to solar system to low multiversal.
Don't go for his innocent face; Rimuru Tempest is one of the strongest anime characters who can easily defeat Saitama. Saitama can handle enemies in hand-to-hand combat easily, but what about an enemy with magical powers? The list of Rimuru's powers is endless.
The mere comparison of strength between the two characters is crazy. Goku is an extraterrestrial being who has to lose a fight in order to get stronger. Saitama is a man that can defeat any foe with a single punch. If the two of them were to face off in a one-on-one battle, Saitama would easily win.
Though Saitama may be the strongest character in his verse, he can also defeat many characters from other anime verses. There are still a few anime characters who are more than capable of defeating Saitama. Despite his overwhelming strength, he might not stand against a few characters.
However, physical blows without Haki don't work on him due to his rubber body, and the only slashing-style ninjutsu Sakura is shown to know is a scalpel-like blade. With that being her only weapon to hurt Luffy with, it's likely she will lose this fight in embarrassing fashion.
Naruto Possesses Massive Firepower
In his base form, Naruto is immensely strong. However, when he combines his Six Paths Sage Mode and his Kurama Mode, he is stronger than anything Luffy will ever face. Even if Luffy were to get 10 more Gears, he still wouldn't be strong enough to stand up to Naruto in this mode.
Fan theory suggests that Luffy will awaken Gear 6 in One Piece. The concept of Gears was introduced in the Enies Lobby arc of One Piece when Luffy brought out Gear 2 against the CP9 agent Blueno. His skin turned pinkish and heated up, allowing our main character to move faster.
Of course, eventually, Luffy will triumph over Blackbeard and he already has the power to do so. With his Awakened Devil Fruit as well as his Haki, which has been advanced in all three spheres, Luffy possesses the power to beat Blackbeard.
1) Kaido. Kaido did in fact lose to Luffy's Gear 5 at the end of the Wano Country arc. However, keep in mind that he withstood multiple waves of strong enemies before this final encounter. Luffy was also completely worn out after the fight and fell into a coma for about a week.
When Luffy uses this power, also known as Gear V, he can transform everything around him into rubber, giving absolute control of his surroundings. Not even Big Mom's strongest attacks would affect Luffy in this state.
Thus, it is safe to say that Limit-breaker Saitama cannot beat Goku in his Ultra Instinct form. It is far too powerful a transformation to contend with. Even if Bald Cape lands his Zero Punch, Goku has been seen multiple times being more than capable of taking a hit.
Luffy is capable of fighting with planetary characters. His fruit doesn't allow him to cause mass destruction tho. Don't think One Piece will ever reach planetary level.
Luffy has been training with his devil fruit since he was a child. Not only does he have YEARS and years on Deku in experience. Take away haki and take away Luffys devil fruit ability and based on skill alone he could still beat Deku with both arms behind his back. Manga Deku is stronger then anime Deku.
5 Shortened Life
While this could likely be a result of the long and hard-fought battle with Kaido on Onigashima and his way up to it beforehand, it could also imply that Gear Five has the biggest strain on Luffy's body out of all.
After all, its true powers could only be revealed once it awakened. However, thanks to Luffy's incredible creativity, this fruit ended up awakening and granted him the power of Gear 5. Essentially, Gear 5 is Luffy and his very best since in this form, he becomes the Warrior of Liberation.
More Freedom. Luffy is the embodiment of freedom in One Piece and Gear 5th takes this quality of his to the absolute fullest. Gear 5th Luffy has been described as "the warrior of Liberation." According to the Gorosei, he spreads laughter wherever he goes and fights with incredible freedom.