Being the assigned navigator of the Straw Hat Pirates, Nami is responsible for evaluating the direction that the ship goes as they sail further into the sea. Nami also tends to act as the crew's de facto treasurer, managing the crew's money and allocating spending money whenever they arrive at a new location.
Nami is an accomplished and agile polearm user. Knowing she lacks the raw strength of most of her crewmembers, she uses her cunning and specially designed weapons to combat opponents who are her physical superiors. While she tries to avoid combat as much as possible, when the need arises Nami gives her all in battle and has defeated some fearsome fighters.
Despite being one of the weakest members of the crew, Nami nonetheless possesses a strong enough will to be able to withstand a burst of Big Mom's Supreme King Haki just like the rest of her crewmates.[20]
Physical Abilities
Nami had spent several years from her tender childhood to her young adult life stealing money from numerous people including dangerous pirates to buy back her village from the Arlong Pirates. These harsh and sometimes brutal experiences granted Nami a very high level of physical capabilities. In the Water 7 Arc, she demonstrated exceptional agility and incredible leg strength, being able to jump the wide distances between rooftops in Water 7. Nami is also physically very strong and fit, and when she is extremely enraged, especially from Luffy's reckless spending, she can pack extremely powerful punches to give vicious beatings, which can cause Luffy, who is tremendously durable, to have brutal and bloody bruises. (This, however, is mainly a gag for comedy, and not representative of Nami's actual strength) While on Weatheria, Nami showed she was capable of running extremely quickly while carrying both a heavy bag much larger than herself and Haredas with great ease.
Although not as skilled at fighting as a few of her crewmates, Nami is still capable of holding her own against weaker foes. When she was grabbed by a Marine officer Nami brought him down with one savage punch and defeated another Marine with barrage of kicks. In Little Garden, when freed from turning into a wax statue, she was able to incapacitate Miss Valentine with a single hit from her bo, along with Princess Vivi. When she was fighting Kalifa, Nami withstood a Shigan from the assassin despite it being a technique that brought down Paulie, a strong foreman. Nami also survived breathing in the toxins from the Daft Green plant, which is so poisonous it can kill quickly if inhaled repeatedly. Nami survived several minutes before getting the cure. Nami has also supported Luffy in an 11-hour fight with Charlotte Cracker, one of the Sweet Commanders of the Big Mom Pirates, which shows that she has high levels of endurance.
Nami was also shown to possess great skill with a bo staff which she would often use for self-defense before acquiring the Clima-Tact. However, because she was usually outmatched by the monstrous foes that they met at sea, she typically relied on her crewmates to fight in her place. Nami also appears to have great skill with ropes, being able to tie up and capture Luffy from behind.
After the two years of extensive training on Weatheria, Nami's physical abilities have vastly improved along with her fighting skills with the Clima-Tact, now capable of handling tougher opponents on her own. An example of this is seen when she has gained significantly high amount of superhuman strength able to easily deflect a sneak attack from a fish-man, who possess ten times the strength of a regular human. Most notably, Nami's dexterous skill with the staff was shown when she reacted to a weakened Wanda's attack before Sanji and Brook were able to save Nami from having to defend herself. After stopping Wanda in her tracks and overpowering her, Nami then managed to pin the weakened mink to the ground.[21] Nami also managed to defeat Brûlée, a moderately powerful daughter of Big Mom. She managed to survive a headbutt from Ulti although Nami noted that another would kill her.
Nami has also shown her already exceptional agility has greatly improved from two years of training as she was able to swiftly dodge Wanda's attack by somersaulting with great ease. She still has limitations however, as when Sanji was trying to outrun Smiley's gas he noted her body could not keep up with the pace of Zoro, Brook, and Kin'emon for long, until he touched her breasts and got a speed boost from over-excitement.[22]
Navigation and Cartography Expertise
Nami is a highly skilled navigator and an extremely talented cartographer. Arlong considered her skills on par with the fish-men "superiority" since they were superior to any fish-man's. When Luffy destroyed her room at Arlong Park, both bathymetric and geographicmaps were seen, proving that Nami has a wide variety of cartographic skills.[23]
She is capable of formulating advanced equations in mere minutes to predict a precise course of action, although she usually needs to write the equations down on a physical medium when formulating them. She has a supernatural ability to sense changes in the weather, "with her body" according to Vivi, and can even predict the emergence of supposedly unpredictable cyclones in the Grand Line, undeterred even by a high fever. This ability, combined with her years of knowledge in cartography and navigation, has also made Nami an expert in meteorology. Not only has she been shown to continuously and accurately predict various normal weather conditions, but she is also capable of predicting and handling the almost unnatural, unpredictable, and inexplicable weather conditions of the Grand Line, being more than capable of navigating through these conditions.
This attribute proved useful during Nami's one-on-one altercation with Enel, where she managed to deflect several of the Goro Goro no Mi user's lightning-based attacks using only "Thunder Balls" from her first Clima-Tact. It could be assumed that after the timeskip, her navigation skills have greatly improved due to her study of the New World climate with the help of Haredas, as even Caribou immediately recognized and praised her skills as a navigator during their descent to Fish-Man Island.
Skilled Thief and Pickpocket
Apart from her navigational skills, Nami has also proven herself to be an excellent thief and a master pickpocket. She is able to take small items, such as keys, without her victims noticing, a skill she honed from a young age. For example, while Wapol was chasing her inside Drum Castle, she managed to steal the arsenal key from his belt without him noticing, hoping it was the key to some treasure vault.[24]
One of her most notable thieving feat was shown just before she left her village. At the harbor, she stole numerous wallets from the villagers saying goodbye to her while she was running past them, and among the villagers and the Straw Hats, plus Johnny and Yosaku, no one noticed until she revealed what she had done.[25] Perhaps her greatest thieving feat is stealing Zeus, one of Big Mom's most powerful Homies, from her.
She now uses this skill to steal from other pirates, and occasionally government employees, more often than not sneaking aboard their ship or base and taking all their valuables while they are distracted by some fight. Her skill at thievery has even been recognized by the World Government and has earned her the epithet "Cat Burglar".
Financial Expertise
Nami has strong memory when it comes to finances since she is mainly handling the Straw Hats' financials due to her fondness of money. While shopping, Nami tends to negotiate as seen during the Return to Sabaody Arc where Nami demanded a discount over the clothes that she attempted to buy at a fashion shop, much to the shopkeeper's chagrin. As seen at Water 7, she can be skillful in a financial negotiation as she skillfully negotiated with the bank staff in giving 300,000,000 for Skypiea's treasure instead of the initial offer of 100,000,000. She also demanded 1,000,000,000 from Vivi for their co-operating on Whisky Peak, but later decided to give up on it for the sake of friendship between her and Vivi after the Arabasta Civil War ended.
Negotiation
Nami is a very convincing person, so much so that she has shown herself to be quite the negotiator in her own right. She has shown to be able to negotiate on behalf of most of the Straw Hats, although most of the negotiations are charged with financials or anything else that would be for her own benefits. Although she mostly handles the financial negotiations, she also able to negotiate in other aspects especially when the Straw Hats do not have much to bargain with, such as making some relationship with others and also keeping the Straw Hats cool during negotiations. As a result of this, one of the biggest benefits is that Nami is usually able to manipulate people and obtain more information on her own. She is able to achieve great things with this skill.
Examples of this include her manipulating Luffy and the crew into trusting her so she could steal the Going Merry, negotiating with Vivi at Whisky Peak on matters involving her protection from Baroque Works agents, her negotiation with the bank staff at Water 7, tricking and befriending Lola's zombie, easily manipulating the residents of Weatheria into forgiving her earlier escape attempts and thefts, and even convincing them to give her a house and other various things so she could stay on the island to train for two years. In addition to the latter, she also managed to convince Haredas to teach her more about the Weather Balls and the changing climates and weather patterns of the New World during her two years of training, despite the fact that she had previously taken him hostage in order to get off Weatheria. More recently, she used her Vivre Card to force the homies in the Seducing Woods to help and protect herself and Luffy against Cracker. She later blackmailed Kingbaum into helping the Sanji Retrieval Team escape from the Big Mom Pirates after the wedding. She also used Zeus' gluttony for her lightning clouds as a bargaining chip to make Zeus become her servant and later took advantage of his attribute as a cloud to force him to discharge massive amounts of lightning at Big Mom herself twice.
Nami wielding her Sorcery Clima-Tact after the timeskip.
Nami's fighting style focuses mainly on using the Clima-Tact to manipulate the weather of her surroundings, also known as the "Art of Weather". When combined with her immense knowledge of meteorology and weather systems, this ability can be used for devastating results.
Nami first gained the ability to manipulate the weather when Usopp gave her the Clima-Tact. The flaw with his invention, however, was that it was primarily for party tricks.[26] Regardless of this conflict, due to her expertise she was able to combine several of its functions in order to pull off dangerous and useful techniques, like creating a mirage of herself, (Mirage Tempo) in order to distract her opponent,[27] and a powerful lightning cloud (Thunderbolt Tempo), which was used on Miss Doublefinger,[28] who thought she was a magician.
After the Skypiea Arc, Usopp improved the Clima-Tact with Dials, creating the Perfect Clima-Tact. This improvement gave her much greater power over the weather, allowing her to easily pull off stronger and newer versions of the tricks she could do with the Clima-Tact, like creating duplicates of herself using mist (Mirage Tempo: Fata Morgana). This weapon was also powerful enough to allow her to wipe out hordes of Marines with Thunderbolt Tempo and defeat CP9's Kalifa with Thunder Lance Tempo. There was still a flaw in its use, however, as Nami was unable to properly control the lightning and her allies would sometimes sustain collateral damage.
After the timeskip, her abilities are greatly enhanced, being able to easily destroy a bar and a submarine (and harm the occupants of both) with lightning blasts that can be compared to an attack by Enel. At the stand-off between Neptune's soldiers with Usopp and Brook, she wielded the upgraded version of the Clima-Tact with the disappearance of the balls, which she now calls the Sorcery Clima-Tact. When the Straw Hats arrived at Gyoncorde Plaza, Nami's "Mirage Tempo" was shown to have improved to the point of making herself appear completely invisible, and she was also able to shoot a powerful gust of wind she named Gust Sword to easily dispatch a fish-man.
She can now use and create weather in more creative ways, like launching an egg which hatches to release a large thundercloud that she can then take control of in order to strike down her opponent(s), which she calls "Thunder Breed Tempo", and creating an orb at the end of one of the three segments of her Clima-Tact which possesses enough heat to melt snow and harm a snow woman like Monet (Heat Egg). This new Clima-Tact has also been proven to not only be useful for battle situations, but regular daily uses as well, such as taking showers (Shower Tempo) and making paths for travel with sea clouds (Milky Road). The latter is an achievement of its own as sea clouds were shown not to be produced in the Blue Sea.[29]
It is unknown how Nami utilizes the abilities of her new Clima-tact as she rarely spins or shakes her weapon to achieve the desired effects, usually achieving her goal after some verbal queue which names the attack. Most notably, Nami seems to have much more freedom in her control of the phenomena she produces as she was able to direct lightning like a projectile in order to hone in on Baby 5 and Buffalo in the sky, as well as move a thundercloud over the guys who were attempting to peep on her while she bathed, and electrocute them, almost cognitively. Her skills at manipulating the weather have increased to such a point that it appears like she is using magic or ninjutsu, but she herself stated that it is simply chemistry.
Second Model
After being further upgraded due to Usopp's Pop Greens and Franky's genius, Nami's new Sorcery Clima-Tact[30] is now the "culmination of all of Weatheria's weather science". The Clima-Tact can now grow or decrease in length when different amounts of pressure are applied, and is easier to twirl and use. It also seems to leave patterns in the air when it is used, overall giving it the feel of a magic wand of sorts. Ironically enough, the only Weatherian device that Usopp failed to implement into the upgraded Clima-Tact was a "magic wand" that he did not quite understand.[31]
After capturing the thundercloud Homie, Zeus, Nami could use her Clima-Tact to store Zeus inside. When necessary, she could use Zeus supplemented with her Clima-Tact abilities to perform destructive lightning attacks. After Big Mom reclaimed Zeus, she lost control of him. After creating Hera, Big Mom abandoned Zeus and the new Homie tried eating him and the thunderclouds Nami tried feeding him, seemingly devouring both.[32]
Having escaped from Big Mom, she heard her Clima-Tact talking to her and found that Zeus' face had attached onto it,[33] eventually learning that Zeus' soul now resides within the Clima-Tact. With the Sorcery Clima-Tact now a sentient weapon, this further enhances its abilities of Zeus being able to change the Clima-Tact to more combat-oriented forms to help aid Nami and can temporarily transfer his consciousness to the clouds that Nami summons, which not only allows him to take on a similar appearance to his former cloud form, but also enables him to take control of Nami's attacks, making them harder to avoid.[34] This power allowed Nami to produce lightning destructive enough to finally defeat Ulti, the immensely durable Tobiroppo, in one strike (Raitei).
Other Techniques
Though infrequent, Nami has a couple of other moves that she can use to incapacitate (in more ways than one) her opponents.
Shiawase Punch (幸せパンチ,Shiawase Panchi?, literally meaning "Happiness Punch"): a joke technique that Nami uses to dispatch people watching her bathe; she simply drops her towel, causing everyone in the vicinity to collapse from a massive nosebleed. She also uses this as a get-rich-quick scheme, as she charges 100,000 to anyone who sees her doing this.[35] This is called Happiness Punch in the FUNimation dub.
In Wano, there was a time she dropped her towel on accident and was genuinely embarrassed by it, but Sanji, who was nearby and invisible due to his Raid Suit, saw her and shouted out the technique's name.[36]
Impact (衝撃貝,Inpakuto?, literally meaning "Impact Shell"): Nami uses an Impact Dial to absorb attacks and then send them back at her opponents. Since she does not have a lot of strength she suffered from the drawback of the Impact Dial. This was shown only when she finished off Hotori with Gan Fall.[37] This technique retains its name in the FUNimation dub.
Mirai Kick (未来キック,Mirai Kikku?, literally meaning "Future Kick"): Nami delivers a roundhouse kick. This was first used on Usopp when he insulted her thoughts of finding "future treasure" on Egghead.[38]
↑One Piece Manga and Anime — Vol. 2Chapter 9 (p. 2) and Episode 5, Nami is introduced as a pirate thief in her infobox.
↑One Piece Manga and Anime — Vol. 91Chapter 921 (p. 6-7) and Episode 911, Nami is tasked with becoming a Kunoichi as her cover while infiltrating Wano Country.
↑ 12.012.1One Piece Manga and Anime — Vol. 45Chapter 435 (p. 16-17) and Episode 320, Nami's bounty for attacking Enies Lobby is revealed along with the other crewmembers'.
↑SBSOne Piece Manga — Vol. 4 (p. 28), Nami's age is revealed.
300,000,000 for Skypiea's treasure instead of the initial offer of 
100,000 to anyone who sees her doing this.[35] This is called Happiness Punch in the FUNimation dub.