Monkey D. Luffy is the captain of the Straw Hat Pirates. He started his journey many years ago, and over time, he became one of the most well-known pirates in the entire One Piece world. Luffy is a very emotional person, so most of the decisions that he makes are based on his feelings.
Throughout One Piece, Luffy has shown that he is more concerned about what is right instead of making the smart choice. While most of his decisions have turned out to be okay, there are times when his decisions have backfired massively and created problems for him and his crew.
5 Attacking The Celestial Dragon
Sabaody Archipelago was the final stop of the Straw Hats before they went into the New World. They were supposed to get their ship coated so that they could head to New World. After Luffy and co. found out that Camie was taken captive, and she was going to be sold at the Auction House, they started to look for her.
When they finally found her, she was being held captive inside a huge fish bowl, which made all of them angry, especially Hachi. The fishman decided to talk to Charlos, but the latter was repelled by him and shot Hachi. After shooting Hachi, Charlos paraded around and this made Luffy furious. So, he went up to Charlos and punched him in the face, which was the right thing to do, but not a smart one. This resulted in Admiral Kizaru coming to Saboady Archipelago, and he almost killed all the Straw Hats. They were only saved due to Rayleigh's intervention.
4 Asking Usopp To Leave
The fight between Usopp and Luffy was incredibly painful to watch because they are really close friends. The fight started after Usopp asked about Going Merry and the money that had been stolen. Luffy tried to change the topic by saying that the crew will get a new ship, but Usopp was against this decision.
After a lot of bickering, Luffy finally told Usopp that the Going Merry could not be fixed, so they had to leave it behind. Usopp was not ready to accept Luffy's decision and this caused a brawl to break out between the two. Usopp continued to say bad things to Luffy, which caused the latter to snap, and he asked Usopp to leave the crew if he didn't agree with the decision. After hearing Luffy's words, Sanji immediately kicked Luffy, which made the latter realize that he made a mistake. There is no denying that Usopp was in the wrong, but Luffy shouldn't have asked him to leave.
3 Challenging Kaido
Kaido is one of the Yonko and the captain of the Beasts Pirates. He is considered to be the "Strongest Creature in the World." He earned his title due to his strength alone. Kaido ruled over the Land of Wano, and he was the first Yonko that Luffy targeted after the time-skip.
When the Straw Hats finally arrived in Wano, they were shocked to see the condition of the place. Kaido's armament factories had robbed the land of all its beauty. The people of Wano were struggling to get their hands on clean drinking water. Luffy's meeting with O-Tama enraged him to the point, where he promised her that he will take down Kaido. While Kaido was rampaging in Kuri, every Straw Hat except Luffy was in the ruins of the Oden Castle.
In a desperate attempt to stop Kaido's rampage, Hawkins told him the location of the Straw Hats. This enabled Kaido to attack the ruins, and in his mind, he believed that the Straw Hats were dead. Luffy also saw this, and he decided to attack Kaido, but it turned out to be a horrible mistake.
2 Facing The Three Admirals On His Own
The Marineford arc is undoubtedly one of the best arcs in the entire series. It focused on the war between the Whitebeard Pirates and the Marines. The war started after the Marines announced that they would be executing Portgas D. Ace. After overcoming multiple problems, Luffy finally managed to arrive at Marineford with the other escapees.
Shortly after his arrival, it became clear that Luffy was punching above his weight. Most of the characters at Marineford were much stronger than Luffy, and he had to be protected multiple times by other people. To make things worse, Luffy decided to attack the three Admirals on his own. Luckily, Luffy did not sustain any serious injury when facing all three of them at the same time.
1 Trying To Fight Magellan
As soon as Luffy heard the news about Ace, the former immediately decided to rescue him. Luffy knew that if he hurried, then he could get Ace out of Impel Down. It was a risky move, but Luffy decided to go ahead with the decision anyway. During his invasion, Luffy had the face multiple opponents, but the biggest threat among them was Magellan.
While fighting Magellan, Luffy nearly died because of the poison. The poison from Magellan's devil fruit completely overwhelmed Luffy, and he was left on the brink of death. He only managed to survive because of Ivankov, who used his power to nurture him back to health.