The world of anime is filled with iconic, dynamic duos: Goku and Vegeta's rivalry in Dragon Ball, Gon and Killua's friendship in Hunter x Hunter, and the never-ending mission of Naruto's search for Sasuke in Naruto. When a hero obtains power, it's usually the result of a rival or friend cheering them on. Oftentimes, these duos are responsible for their partner's preservation, saving each other time and time again.
However, there are many protagonists who prefer to work alone; by doing everything solo, they pay the price for forgoing partnership. If they simply swallowed their pride and accepted help, their efforts might've led to completely different outcomes, many of which are preferable to the ones they got.
10 L's Left-Hand Man Needed To Not Be Kira (Death Note)
L was the world-renowned detective tasked with finding Kira in Death Note. He became suspicious of Light Yagami after deducing Kira was a student from the Kanto region with connections to law enforcement. L hoped to observe him by allowing Light to join the Kira task force, but L was later killed through Light's nefarious manipulation of a shinigami.
Despite L's incredible intelligence, he failed to consider the consequences of choosing Kira as his protégée. Light was given access to all information regarding the investigation, enabling him to plan ahead. Had L chosen to rely on Watari, Soichiro, or any other task force member, he might have discovered Kira's identity and lived to tell about it.
9 Carrion Refused Rimuru's Help Against Milim & Frey (That Time I Got Reincarnated As A Slime)
Carrion was the king of Beast Kingdom Eurazania and one of ten Demon Lords in That Time I Got Reincarnated As A Slime. Following Demon Lord Milim's declaration of war, Carrion evacuated his citizens, but he remained behind to defend his country alone. Milim defeated him quickly, destroying the capital city with a single blast while Demon Lord Frey captured Carrion.
Even without Frey's interference, Carrion was no match for Milim; had he invoked Rimuru's help or fought alongside the Beastketeers, Carrion might've effectively protected his city and warded Milim off. Due to his refusal to ask for help, Carrion was single-handedly responsible for the destruction of most of Eurazania.
8 Team Avatar Failed During Korra's Clash Against Unalaq (The Legend Of Korra)
During Book Two's climax in The Legend Of Korra, Unalaq freed and fused with Vaatu to become the Dark Avatar. Revealing his intent to subjugate the world and rule as its king, Korra was forced to defeat him using spiritual energy; but as a result of their battle, she lost her connection with the past Avatars.
Despite Korra's role as Avatar, she didn't need to face Unalaq alone. Team Avatar might've tipped the balance had they arrived in time to prevent the villain's fusion, but when she needed them most, they'd vanished. If they'd done their duty to the world, Unalaq would've posed no threat to it and Korra's controversial severed connection could've been avoided.
7 The Akatsuki Popped Utakata's Bubble While He Traveled Alone (Naruto Shippuden)
Utakata was a rougue jinchuriki from Kirigakure in Naruto Shippuden. He worked with Naruto to save his student, Hotaru, from an explosive jutsu. After finally becoming Hotaru's master, Utakada returned to Kirigakure to rejoin Kirigakure, but he was killed en route by the Six Paths of Pain.
Despite being the Six Tails, Utakata proved no match for Pain, only managing to destroy two of the six before being defeated. Utaka might've escaped had he allowed Hotaru or Naruto to accompany him to Kirigakure; his survival would've effectively prevented the resurrection of the Ten-Tails and the Fourth Great Ninja War.
6 The Androids' Assistance Would've Prevented Piccolo's Defeat (Dragon Ball Z)
In Dragon Ball Z, Piccolo was forced to fight Imperfect Cell after the latter located Androids 17 and 18 and attempted to absorb them. Piccolo used his newfound power as a Super Namek to prevent Cell from achieving his Perfect form, but he failed; battling alone, Imperfect Cell quickly overwhelmed him, broke his neck, and threw him into the sea.
Piccolo's fate could've been avoided if his on-lookers had helped; instead, they watched the one-sided battle unfold without sending so much as a ki-blast Cell's way. Despite 16 stating that Cell's power was equal to Android 17's, neither considered joining the fray to overwhelm Cell. As a result of this egregious mistake, Cell destroyed 16, absorbed 17 and 18, and achieved Perfect form.
5 Goku Bungled Buu's Defeat By Refusing Fusion (Dragon Ball Z)
After Buu destroyed nearly all life on Earth, Goku and Gohan were the only Earthlings left. Their chances for victory improved when Gotenk's fusion ended inside Buu, resulting in a steep decline in the Majin's power. The Saiyan duo also possessed the Potara earrings, which allowed two people to fuse and combine their power.
Yet when Gohan was finally ready to don the earring, Goku opted instead to fight alone. In another stroke of Saiyan hubris, Goku's inability to work effectively in a team resulted in Gohan's absorption and an immense spike in Buu's power. A desperate fight for Earth's salvation ensued, but it could've been avoided had Goku swallowed his pride and fused for a mere hour.
4 Defending Damaged Demon Slayers Got Kyujiro Killed (Demon Slayer)
Kyujiro Rengoku was the Flame Hashira in Demon Slayer. He made his debut in the Mugen Train arc, fighting two of the Twelve Kizuki. He was forced to defend an injured Tanjiro alone against Akaza, the Upper-Rank Three, and happily gave up his life defending his injured allies.
Despite Kyujiro's power and ability to parry Akaza's blows, he reached his limits due to the demon's regenerative abilities. Tasked with fighting defensively, Kyujiro put his life on the line for Tanjiro and Inosuke. Had the two not been incapacitated, they might've assisted in finishing Akaza in time. However, they failed to reach the demon before it broke Kyujiro's grip, effectively rendering the Hashira's sacrifice meaningless.
3 Netero Needed Zeno's Assistance Against Meruem (Hunter X Hunter)
Netero was the Chairman and one of the strongest Hunters alive in Hunter x Hunter. He faced Meruem, the Ant King, when the latter launched his plan to destroy humanity. After the Bodhisattva Zero Hand failed to kill him, Netero used the Poor Man's Rose to defeat Meruem, triggering an explosion that guaranteed their mutual deaths.
Meruem discovered the secret to Netero's 100-Type Guanyin Bodhisattva by studying his movements during their fight. Had Zeno Zoldyck accompanied Netero, Meruem would've had to contend with two opponents, effectively splitting his attention. This would've prevented Netero from losing his arm and leg, as well as enabled them to devise a strategy that didn't require self-sacrifice.
2 LeMillion Lost His Quirk While Deku Was Distracted (My Hero Academia)
Mirio Togata, or LeMillion, was the leader of The Big Three in My Hero Academia. LeMillion risked his life protecting Eri from Overhaul, the leader of the Shie Hassaikai. He used his quirk, Permeation, to battle Overhaul with near-invincibility and almost won. However, he sacrificed this ability to save Eri from a quirk-erasing bullet.
Despite LeMillion's advantage against Overhaul, he lost due to being partnerless; it was impossible to attack Overhaul and defend Eri effectively simultaneously. Deku failed to reach LeMillion in time. If he had, Deku could've used One For All to remove Eri from battle, enabling LeMillion to use his quirk at maximum efficiency to defeat Overhaul.
1 Jiraiya Would've Lived If He'd Listened To Tsunade (Naruto Shippuden)
Jiraiya was one of the Legendary Sannin of Konohagakure; he spent much of his time tracking the movements of Konohagakure's major enemies, including Orochimaru and the Akatsuki. He journeyed alone to Amegakure to find the Akatsuki's leader, battled valiantly against him, and successfully learned the secret of the Six Paths of Pain before his tragic defeat.
In choosing to face Pain alone, Jiraiya went directly against Tsunade's orders despite her position as Hokage and refused her offer to accompany him. As a fellow member of the Sannin, Tsunade's assistance would've turned the tide of battle. Renowned as the world's strongest kunoichi and its greatest medical ninja, Tsunade's power would've offset the duo's disadvantage in numbers.