Sailor Moon is filled with numerous superheroines who never turn their back on their friends, never run from real fights, and battle evil by moonlight. But there are times when the Sailor Senshi (or Sailor Guardians) have been less than perfect.
Sometimes, they are careless, selfish, and risk letting horrible things happening. Now, usually, everything works out in the end, with the villains destroyed and the heroes victorious, but there are times when it feels like they are really lucky that things worked out in their favor.
In Sailor Moon, the Sailor Senshi all have at least one greatest failure, some more than others.
10 Sailor Chibi Moon: Losing The Silver Crystal
After dealing with bullies or getting yelled at for breaking a vase, depending on the manga or anime, Chibi-Usa took the Silver Crystal to use its power, causing it to disappear within her body. And it takes her a season to cry it out again. This was not very timely, since the Black Moon Clan was attacking. The villain Wiseman was even able to use her shame over what happened to transform Chibi-Usa into the villainess Black Lady. Under this new form, she even committed other crimes, including being partially responsible for Saphir's death.
9 Tuxedo Mask: Not Telling Usagi About His Nightmares
In Sailor Moon R, Mamoru starts having nightmares where Usagi dies if he and her continued on as a couple. Mamoru was understandably scared for Usagi's life, but the worst part of this was his not telling her about them. Instead, Mamoru breaks up with her and leaves Usagi feeling as if she did something wrong.
The right thing to do would have been telling Usagi the truth and, as a couple, worked out to go from there if Mamoru's nightmares were in fact a prophecy. As it turns out, the dreams were a test created by King Endymion to test his past self and Usagi's love.
8 Sailor Moon: Refusing to Sacrifice Hotaru
Being who she is, it's not all that surprising Usagi, or Sailor Moon, has made some mistakes. She was fourteen-years old when she became a Senshi, after all. However, her greatest failure in the '90s anime is also easily her most shining moment.
When Sailor Moon learned Hotaru was really both Sailor Saturn and Mistress 9, she still refused to sacrifice her life in order to save the entirety of Earth. This drove a rift between Sailor Moon and the Outer Senshi. When Moon finally gave Mistress 9 the Holy Grail (or Moon Chalice), she about near guaranteed the end of the planet. Not too long after, though, Moon made good on her optimism by saving everyone as well as Hotaru from Pharaoh 90's advent.
7 Sailor Mars: Not Treating Sailor Moon Right
This is harsh, but Sailor Mars wasn't the ideal Sailor Senshi for most of the first season of the classic anime. She showed up to the fights and took down the enemies, but she wasn't cooperative with her very own teammate, Sailor Moon.
Everything changed when it was revealed Usagi was the Moon Princess and Mamoru was Prince Endymion, though. The shock of everything — including seeing Mamoru on death's door after being impaled by Zoisite — caused Mars to react poorly to Moon's emotional outburst following her learning she was Princess Serenity. Mars slapped Moon in a fit of rage that was really a sign of her own issues. Before this all happened, Rei was "dating" Mamoru; she had unreciprocated feelings for him that were deeper than everyone realized. So, when Mars heard Moon's "tantrum" — he jumped in harm's way to save Sailor Moon from Zoisite, after all — she took that as Moon not appreciating his sacrifice. This also meant Mars had to give up her overlooked feelings for Mamoru as Princess Serenity and Prince Endymion were now endgame. Ultimately, this ordeal made Mars feel more protective of Moon, and the two became incredibly close.
6 Sailor Saturn: Not Killing Sailor Galaxia
Being the Senshi of Ruin, Sailor Saturn can destroy worlds with one drop of her Silence Glaive. Yet in episode 197 when Saturn confronts Galaxia, she doesn't do anything but get distracted by the enemy's revelation — she released Queen Nehalennia so that Saturn would be reawakened and to complete Earth's team of Sailor Senshi once again. This way, Galaxia could then steal all of their true Star Seeds.
Saturn gets so caught up in Galaxia's story that she fails to do what she's destined to do — destroy great evils. Galaxia ultimately breaks the Glaive, thus rendering the Senshi powerless. Had Saturn just killed Galaxia there, maybe things would have been different.
5 Sailor Venus: Getting Katarina Involved
When Minako Aino was based in London fighting the Dark Kingdom's forces, she became close friends with an Interpol officer named Katarina, even revealing herself as Sailor V. Involving her turned out to be a mistake in hindsight, as the villain Kunzite found her and transformed her into a Youma in an attempt to destroy the Sailor Senshi.
On a related note, Minako revealing that Sailor V and Sailor Venus are indeed the same person in front of Zoisite and Kunzite was probably not such a good idea, either.
4 Sailor Neptune: Giving Into The Evil Puppet
When an evil puppet captures Sailor Uranus and Sailor Neptune comes to her rescue, the puppet threatens to release evil shadows onto the world that might kill the human race if she attacks. So, Sailor Neptune attacks. While it's possible that she called the puppet's bluff, she was a little too willing to risk destroying humanity and could have doomed the world if he was telling the truth. Given her and Uranus' track record of wanting to sacrifice people for the greater good, she was also kind of a hypocrite.
3 Sailor Uranus: The Failed Galaxia Plot
When it seems like Galaxia is probably going to succeed in her plans, Uranus and Neptune decide to join the winning team. So willing to prove their loyalty, they go so far as to kill Sailor Pluto and Saturn. It turns out that the whole scheme was just an attempt to get close to Galaxia so they could take her down directly, but it backfired horribly when it turns out her Star Seed was not within their body. The problem was that Uranus and Neptune didn't tell their teammates about their plan, and the betrayal stung even after the reveal.
2 Sailor Star Maker: Leaving Ami To Die
When the Phage Sailor Gamer is released upon the world in a Sailor Stars episode, Sailor Mercury is the only Senshi ready to stop her. But she's not the only one available: Taiki is in the same room as her but just walks away, leaving Ami to her fate. And this isn't one of those "going in the next room to transform" deals; Ami and Taiki previously had a fight over Usagi, but leaving her to die is a bit of an overreaction. Even Seiya calls out Taiki on this, encouraging the Starlights to help.
And while the Inner Senshi hope to distract the monster long enough for Sailor Moon to arrive and change her back to normal, Taiki completely planned on killing the Phage and once again had to be talked out of it by Seiya.
1 Sailor Pluto: Not Stopping The Black Moon Clan
Sailor Pluto is the Sailor Senshi of time and space. Appointed by Queen Serenity, she guards the Space-Time Door and was warned not to leave her post, stop time, or travel through time, on the pain of losing her life. She seems willing to break these rules if the other Senshi need her, but her powers do bring up an interesting question. During the second story arc, the villains, the Black Moon Clan, have time-traveled from the future and are attacking the Senshi in their present. Given that Sailor Pluto has the power of time on her side, was there really nothing she could do to keep the enemies in their own time? Preventing villains from time-traveling seems like the whole reason there was a Space-Time Door to begin with.