Monkey D. Luffy is the main character of Eiichiro Oda's One Piece. With the aim of becoming the Pirate King, Luffy set out to sea and acquired a very powerful crew, called the Straw Hat Pirates. Over the years, the protagonist has acquired tremendous fame and power, and currently, he's considered to be one of the greatest pirates to ever live.
That certainly doesn't mean Luffy hasn't made mistakes, however. On his way to the top, Luffy made several errors and without the help of his crewmates, he wouldn't have come as far as he has.
7 Attacked Zoro On Whiskey Peak
Luffy is generally a person who always trusts his crew over anyone. In Arlong Park, he trusted Nami despite her being adamant that she had betrayed them. In Water 7, Luffy didn't believe a word that Robin had to say to him, and he even followed her to Enies Lobby.
On Whiskey Peak, however, Luffy acted rather strangely. When Zoro protected the crew by cutting down 100 bounty hunters, Luffy attacked him, thinking he killed the people who gave them food. Even though Zoro tried to explain his side repeatedly, Luffy made sure not to listen and kept attacking him, until Nami stopped the two for good.
6 Didn't Act Like A Captain At Drum Island
Shortly after leaving Little Garden, Nami fell to a very serious disease called Kestia. To find a doctor for her, the crew ended up going to Drum Island. Unsurprisingly, the people of Drum Island weren't too keen on letting pirates enter their country, especially after Blackbeard, another pirate, had ravaged it recently.
Upon hearing this, Luffy almost resorted to aggression until Vivi intercepted and made him realize that Nami could die depending on what decision he made. Vivi also highlighted Luffy's shortcomings as a captain and eventually opened his eyes to the fact that he should be requesting entry instead.
5 Played A Part In Usopp Leaving The Crew
The Water 7 arc is quite easily one of the best in the entirety of One Piece, and Luffy played a big role in triggering a conflict among the crew during this storyline. After hearing that the Merry couldn't be repaired, Luffy decided to buy a new ship. Usopp, naturally, disagreed and wanted to put his trust in the ship that had carried the crew to the Grand Line.
It goes without saying that Usopp wasn't being rational, however, in the heat of the moment, Luffy made his sniper realize that he should stay behind. Sensing what Luffy was about to say, Sanji kicked him before he could finish his sentence, however, the damage was already done.
4 Thought He Could Meet Up In 3 Days
Perhaps the biggest tragedy that befell the Straw Hat Pirates was on Sabaody Archipelago. After punching a Celestial Dragon, the Marines sent out Admiral Kizaru to the island. At the same time, to deal with the influx of pirates so close to their HQ, they sent Sentomaru and his Pacifistas to hunt them down.
Luffy and the crew attempted to fight anyone they came across, only to fail miserably. For the very first time, Luffy knew he was out of his depth and ordered his crew to run away and meet up in 3 days near Grove 1 of the island. Needless to say, the plan failed because their enemies were too strong and, had it not been for Bartholomew Kuma, the crew could very well have died that day.
3 When He Underestimated The Enemies In The New World
As a captain, Luffy has always been a bit too easygoing, and this was, once again, apparent moments before he set out for the New World. When Jinbe warned Luffy of the threats that lurk in the New World, such as Blackbeard hunting for powerful Devil Fruits or Sakazuki's Marines hunting down the pirates more aggressively, he didn't seem to care, much to the annoyance of the former.
Instead, Luffy's crew listened to everything that Jinbe had to say on his behalf while their captain ate. While this is nothing new for Luffy, one would expect him to listen more carefully, especially after shortly returning from a tragedy that separated him from his crew for 2 years.
2 Thought He Could Beat Kaido In Kuri
Luffy and his crew arrived in Wano Country in order to defeat Kaido and eventually liberate the place from his clutches. Kin'emon, the leader of the Akazaya Nine, laid out a brilliant plan that he believed would increase their chances of taking down Kaido massively.
Unsurprisingly, Luffy abandoned the plan the moment he saw Kaido attack his crew. Instead of recollecting his composure and assessing the situation, like Law, Luffy attacked Kaido head-on and, even worse, believed he could beat the Yonko at the time. The two fought a short-lived battle which ended with Luffy getting one shot by Kaido and then being imprisoned in Udon.
1 Is Terrible With Kids
Luffy's personality is certainly quite interesting, however, he isn't always great with kids. Luffy has proven to be a menace to Momonosuke on various occasions despite him being just 8 years old. Luffy's bluntness is often too much for kids to take. With Tama, Luffy didn't hesitate to mention that Ace had died which subsequently saw her pass out.
On other occasions, Luffy has also fought Momonosuke and beaten him because he felt like it. While that is a part of who he is, it is also hammered home the fact that Luffy isn't the best person to have around kids.