In the Wano Arc of One Piece, Monkey D. Luffy faced off against Kaido, one of the strongest individuals in the world and a former Four Emperor of the Sea. Despite being defeated in their first encounter, Luffy gained valuable insight into how to improve his fighting abilities and trained intensely, honing his advanced Armament Haki (Ryuo) to bypass Kaido's tough defenses. He also discovered the ability to coat himself in Conqueror's Haki, allowing him to finally fight Kaido on equal footing. Finally, the Awakening of his Mythical Zoan Devil Fruit, the Hito Hito no Mi, Model: Nika, gave him the power he needed to overcome Kaido's incredible might. While Luffy's strength is now on par with an Emperor and perhaps even the Admirals, he still has a ways to go before he can challenge the likes of Shanks, the most powerful character in the series. It's likely that Luffy will need one or two more boosts in strength before he can take on Blackbeard or the strongest fighters in the Marines and World Government.
Mastering Gear 5
Gear 5 grants Luffy an unparalleled boost in speed, power, and durability, as well as an absurd level of healing and regeneration. His rubber body's malleability reaches new heights, allowing him to withstand direct attacks from Kaido's Hassaikai by stretching to absorb the force and then returning to his natural state in no time. This regeneration is active even when Luffy is unconscious, indicating that it is his body's base state in Gear 5. Luffy can seamlessly switch between his Gear 2, 3, and 4 forms, and even transform into a giant. However, his most significant power boost comes from his ability to turn his surroundings into rubber, limited only by his imagination. This ability allows him to stretch the very ground itself to block Kaido's Blast Breath and redirect it towards his opponent, showcasing the almost cartoonish nature of his Devil Fruit Awakening. He can even apply this to intangible substances such as lightning, opening up many possibilities for his newfound abilities.
Despite all these advantages, the downside of Gear 5 is its high energy consumption when activated. During his fight with Kaido, Luffy was likely in this state for only a few minutes in the final exchanges of the battle, suggesting that he has not yet fully mastered it. Even after this short duration, he experiences intense fatigue and exhaustion upon reverting back to his normal state, and appears to visibly age in the process. Although he can trigger the state again by altering his heartbeat to match the Drums of Liberation, repeated use of Gear 5 in quick succession will compound the exhaustion and take an increasing toll on Luffy's body. He still needs to get accustomed to the strain of using the form, similar to how he did with Gear 2 and Gear 3 over the time skip, to be able to enter Gear 5 at will without completely draining himself. While the form proved to be effective against Kaido, Luffy has a long way to go before he can use it against even more formidable opponents like Shanks, Blackbeard, or the Admirals in prolonged battles.
Leveling Up His Haki
During his battles with Kaido, Luffy discovered the true potential of Conqueror's Haki and learned to enhance the power of his attacks by coating them with it. Kaido himself acknowledged that Haki triumphs over all other power-ups in the New World, as demonstrated by Shanks, the former Pirate King, and even Kaido himself. Although Luffy's initial use of Conqueror's Haki coating was crude and amateurish, he gradually improved and was able to fight on equal terms with Kaido in their third battle. However, Luffy still has a long way to go to reach the level of Shanks, Roger, or Garp, who could level entire cities with their Conqueror's Haki coating. To achieve this level of power, Luffy will need to undergo serious training to master advanced Haki techniques such as Future Sight, Observation Killing, and the ability to project his will over long distances. It is possible that Luffy may acquire these skills after training with or fighting against Shanks in the upcoming Elbaf Arc, allowing him to challenge the world's strongest in one-off battles and pursue his dream of finding the One Piece.
The Voice Of All Things
Luffy's ability to hear the Voice of All Things remains a mystery and has yet to be fully explored. Similar to the Pirate King, Gol D. Roger, Luffy has demonstrated the ability to hear the voices of Sea Kings and the giant elephant Zunesha, who carries the nation of Zou on its back. However, unlike Kozuki Momonosuke, Luffy was unable to comprehend the information being relayed by Zunesha. The true extent of this ability is still unknown, and it is possible that it may manifest as a means to command Sea Kings, rally armies and allies, or control large groups of individuals and creatures. The final saga of One Piece may hold answers to this and many other questions.