"Red-Haired" Shanks, commonly known as just "Red Hair", is the chief of the Red Hair Pirates and one of the Four Emperors that rule over the New World. Having sailed with the legendary Roger Pirates since he was an infant, Shanks would begin his pirate career on their ship as an apprentice alongside Buggy, before forming his own crew following Roger's death.
Twelve years ago, while operating in the East Blue, Shanks inspired the young village boy, Monkey D. Luffy to go on his own pirate journey, thus being responsible for the boy becoming the notorious outlaw he is today. He accidentally provided Luffy with the Gomu Gomu no Mi to eat, and even sacrificed his left arm to save the boy from being eaten by the Lord of the Coast out at sea. Most notably, he also owned the straw hat that once belonged to Gol D. Roger himself and has become Luffy's signature accessory, having gifted it to the boy as part of a promise for them to meet again someday.
Ever since the beginning of the series, Shanks has been an important background character, usually being shown accompanying Luffy's ever-growing reputation as a pirate. He is a late, but still vital ally during both the Marineford and Wano Country Arcs. He and his crew also have a sizable role in One Piece Film: Red, which centers on Uta, Shanks' adoptive daughter.
As one of the Four Emperors, Shanks is one of the four most powerful pirates in the world, and proof of that is his massive bounty of 4,048,900,000, which is the highest among the current Emperors. According to Buggy, Shanks' immense potential was visible since their days as pirate apprentices in the Roger Pirates, and thought Shanks would succeed Roger as the next Pirate King. While Shanks was not interested in reaching Laugh Tale at the time, he quickly made a name for himself, gaining an impressive bounty of 1,040,000,000 twelve years before the main story. During this time, he competed with Dracule Mihawk, the "Strongest Swordsman in the World", in daily duels that were described as legendary.
It is also important to mention that Shanks was able to reach the rank of Emperor even after losing one of his arms, and is also the only one among them, in the original and current lineup, to not have the powers of a Devil Fruit.
Kaidou, who is renowned as the world's "Strongest Creature", put Shanks in the same elite class as other legendary pirates, that actually possess the strength to stand against him in battle, such as Rocks D. Xebec, Whitebeard, Kozuki Oden, and Roger. As proof of this, he stopped Kaidou from attacking Whitebeard a day before the Summit War of Marineford and later joined Marineford himself a day later. Rockstar also used his captain's name to convey to Whitebeard the importance of the letter he delivered to him. Admiral Akainu fought through Whitebeard's many divisional commanders, two former Warlords of the Sea, and even Whitebeard himself, but did not challenge Shanks when he appeared. Members of the Worst Generation, such as Eustass Kid, Scratchmen Apoo, and Basil Hawkins had to ally with each other to have a possibility of overthrowing Shanks. Admiral Ryokugyu chose to pull back his attempt on Luffy after he realized Shanks was present outside of Wano Country. Another testament to Shanks' strength is that he was able to defeat Eustass Kid, a powerful pirate whose bounty is worth 3,000,000,000 and one of the two pirates responsible for defeating former Emperor Big Mom, with a single attack.
The name Shanks alone commands great power, as Buggy himself proved. His assertion that he previously had a "brotherly bond" with Shanks was one of the many things that earned him respect from the Impel Down inmates. In addition, Buggy did not shy away from using the names of Shanks and his previous captain, Gol D. Roger, to maintain his respect among them. Even the fact that Buggy was seen back talking to Shanks was seen as a testament of Buggy's power to the former prisoners, who were not aware that the two had always acted like this and mistakenly thought that it was because Buggy was not afraid of an Emperor.
Shanks commands enough power to end the war at Marineford with just words. When he stated that there was to be no more fighting, no one stepped up to challenge him, even though the Marines were fired up after the deaths of Ace and Whitebeard. Five Elder St. Shepherd Ju Peter stated that Shanks is one of the few people capable of stopping Blackbeard. This faith was proven valid when Shanks asked Blackbeard if he intended to confront him, he stopped fighting and ordered his crew to retreat, despite having acquired the powers of the Gura Gura no Mi along with his original power, and also strengthened his crew with many of the most powerful prisoners of Impel Down's sixth level. Furthermore, when Shanks requested that Whitebeard and Ace's dignity at death not be violated, Sengoku himself decided to call off the war and offered to take responsibility, showing that despite being a pirate, Shanks has earned Sengoku's respect, something that no pirate other than the late Whitebeard is known to have achieved.
Shanks also possesses enough influence to gain an audience with the Five Elders, who, like the leaders of the World Government, would normally consider him an enemy.
According to Brannew, one of Shanks' greatest attributes is his leadership and charisma, having managed to earn the absolute trust and loyalty of the most talented and capable individuals from the four seas and Grand Line all noted for having particularly high bounties, and recruited them into his crew. The most prominent are his officers: Benn Beckman of North Blue, Yasopp of East Blue, and Lucky Roux of South Blue. This made Shanks' crew extremely well balanced and impregnable, able to contend equally with the enormous military power of Charlotte Linlin's Big Mom Pirates, Kaidou's Beasts Pirates, and Edward Newgate's Whitebeard Pirates.
Shanks is incredibly skilled at infiltration and stealth, as shown when he successfully managed to infiltrate Mary Geoise by wearing only a cloak, a noteworthy feat considering that for most pirates, entering through Mary Geoise without being invited or enslaved is practically considered an impossible and unthinkable feat. He also avoided detection from the many guards and marines present.
Shanks is an excellent swimmer, having once swam deep into the ocean depths to save Buggy from drowning. He is pretty fast at swimming as well, being able to rescue Luffy in the open ocean from a Sea King attack.
Shanks possesses immense physical strength, as he was once a rival to Dracule Mihawk, a master swordsman with tremendous power that could overwhelm Zoro in terms of brute force with immense ease. Even with only one arm, Shanks can apply tremendous power to his swordsmanship, being able to easily match Whitebeard, a gigantic man who could completely overpower giants and an entire army of powerful and skilled Marine officers. With his physical strength combined with Busoshoku Haki, Shanks could defend against Akainu's magma fist, which has extremely destructive offensive power. He also has extraordinary leg strength, as he was able to leap from his ship all the way to the Victoria Punk despite the two ships being miles apart in distance.
Shanks possesses tremendous levels of endurance and tolerance for pain. Even after having his arm bitten off by a Sea King that attempted to devour Luffy, Shanks was completely unfazed despite the heavy bleeding and simply used Haoshoku Haki to scare off the Sea King.
Shanks is also extremely fast, as shown when he intercepted Akainu's attack before he could kill Koby, despite having just arrived at Marineford. On Elbaf, Shanks leaped from his ship to the Victoria Punk in an instant before Kid could fire his Damned Punk.
As the former rival of Dracule Mihawk, the "Strongest Swordsman in the World", Shanks is an immensely skilled swordsman. Prior to losing his left arm, he competed in ruthless duels on a daily basis with Mihawk. Even after losing his arm, Shanks is able to match a blow from Whitebeard, which is a testament to his prowess in swordsmanship He is also powerful enough to easily block Akainu's magma fist using only his sword and Busoshoku Haki. Along with his mastery of Haki, he could replicate the techniques of his former captain Roger, having enough power and skill to defeat both Kid and Killer in a single attack.
Shanks apparently favored his left arm for combat before he lost it, as he is always seen holding his sword in his left hand during flashbacks. As such, he is presumed to have been left-handed or at least ambidextrous before losing said limb
Shanks is one of the very few people in the world who can use all three types of Haki. Even Whitebeard complimented Shanks for his Haki when he used it on his visit, with Jozu stating it was overwhelming.
Haoshoku Haki
Shanks possesses immense mastery in the usage of Haoshoku Haki, a rare form of Haki that only one in several million people in the world can use. It was first hinted sometime after his introduction, before the reveal of Haki, with him intimidating a Sea King with a single glare, causing it to flee for its life. When boarding the Moby Dick, the main ship of Edward Newgate, Shanks was capable of knocking dozens of his men unconscious, many of whom were seasoned men able to survive the New World, while the flagship itself, a ship able to survive the harsh conditions of the New World, was damaged by the sheer force of his presence, impressing those around him.
Shanks' Haoshoku Haki was at least twice as potent as Luffy's by the time of the Fish-Man Island Arc. While Luffy only knocked out 50,000 of the New Fish-Man Pirates, Shanks could have knocked out all 100,000. During the Wano Country Arc, he released a massive burst of Haoshoku Haki that paralyzed Admiral Ryokugyu, stopping him in his tracks from miles away at sea without needing to step foot into the country. Both Jinbe and Yamato stated that such a display of Haki was monstrous.
Non-canonically, in One Piece Film: Red Shanks' Haoshoku is also capable of affecting a few Vice Admirals, causing them to fall to their knees, although Admirals Kizaru and Fujitora seemed unaffected.
Most notably, he is among the small "handful" of people capable of using the advanced application of "infusing" Haoshoku Haki into their body or weapons, his sword Gryphon in particular, as signified by the thin streams of black lightning radiating from it. However, Shanks' use of this ability seems to be much more potent compared to the likes of Big Mom, as he defeated Eustass Kid and Killer in a single Haoshoku Haki-infused attack; the latter took much less of the actual impact, while causing collateral damage to their ship and crew. This is a notable representation of Shanks' power because Kid and Killer both took a number of attacks from Big Mom and her Homies, and both had recovered from their previous battle against the Emperors on Onigashima.
When Shanks and Whitebeard collided, it made the heavens split in half.
Techniques
Observation Killing: An advanced Haoshoku Haki technique that allows Shanks to control his own presence, which prevents others from seeing into the future.
Kamusari is a word used in the Kojiki, where it refers to the passing away of a kami. In the VIZ manga and Funimation adaptations, this is called Divine Departure.
Busoshoku Haki
Shanks is an immensely skilled user of Busoshoku Haki. During the Summit War of Marineford, his Haki-imbued sword easily blocked Akainu's magma-enhanced punch, which was powerful enough to burn enemies such as Ace, Jinbe, and even the Emperor Whitebeard
Kenbunshoku Haki
Shanks is an immensely skilled user of Kenbunshoku Haki. He was able to sense a "weird presence" while he was miles outside Wano Country. He can also use the advanced application that allows him to briefly see into the future, as shown when he saw Kid prepare an attack to eliminate all the ships of his affiliates.
Shanks wields a sword named Gryphon in combat. It is a large saber with a single edge blade and a large hand guard. He can coat his sword in a "fiery" aura and use it against his enemies
Shanks has wielded four different swords at various points in the past aside from Gryphon. He used two different swords during his time as an apprentice pirate aboard Gol D. Roger's ship (one around the time Buggy ate the Bara Bara no Mi and another during a clash with the Whitebeard Pirates) and another one during his stay in Luffy's hometown. He was seen wielding a different sword during his meeting with Ace, which means he obtained Gryphon after the encounter with Ace.