Usagi Tsukino, also known as Sailor Moon, fought many enemies throughout her run in the titular anime. She, along with her fellow Sailor Scouts, saved the world and their friends multiple times, and no matter who they fought, they usually came out victorious.
However, there were some foes that were the toughest to ever for Usagi to fight against. From Princess Snow Kaguya's attempts to freeze the entire world to Chaos itself threatening its own brand of destruction, Usagi had a tough time defeating these enemies. If it wasn't for some help from her fellow Sailor Scouts, or other allies, Sailor Moon would not have been able to defeat them.
10 Princess Snow Kaguya Tried To Freeze The Planet As Part Of Her Collection
Princess Snow Kaguya was the main antagonist of the movie Sailor Moon S, Hearts In Ice. She tried to freeze the entire planet, and she could ride on comets to freeze other planets as well. Despite her being shoved aside in the movie's plot in favor of giving time to Luna (Usagi's cat) exploring a romance with human astronomer Kakeru Ōzora, Kaguya remained a threatening foe, especially after she started taking Kakeru's own life energy.
9 Fiore Was Rivals With Sailor Moon Over Mamoru After Being Corrupted By The Xenian Flower
In the movie Sailor Moon R: The Promise Of The Rose, Fiore was corrupted by the Xenian Flower, an invasive entity that feeds on planets until they blow up. He then sought to take over the planet with these beautiful but deadly flowers as a twisted way to make Mamoru happy.
Fiore was previously friends with Mamoru and even somewhat took care of him after Mamoru lost his parents. However, his inability to stay on Earth long led to him going back into space and trying to find flowers to make Mamoru happy, thus leading to him finding and being corrupted by the Xenian Flower. Despite the tragic backstory, he's an extremely deadly foe. His rivalry with Usagi over Mamoru made him a scary villain for her to defeat.
8 Kaolinite Figured Out Usagi's Identity As Sailor Moon And Had Tuxedo Mask Turned Into A Glass Statue
Even though Kaolinite ultimately died going up against Sailor Uranus in the '90s version of the anime, she was one of the first members of the Death Busters to figure out that Usagi was Sailor Moon. She used this to corner Usagi by using her daimon to turn Tuxedo Mask into a glass statue when he tried to defend Usagi and almost achieved getting Usagi's Pure Heart. If it wasn't for the rest of the Sailor Scouts coming to the rescue, Usagi would have been done for.
7 The Doom And Gloom Girls Killed Usagi's Fellow Sailor Scouts
The Doom and Gloom Girls were some of Usagi's worst enemies. Not only were they tough enemies to defeat in general, but they actually killed all of Usagi's fellow Sailor Scouts in the process. Even though the Doom and Gloom Girls were eventually defeated, Sailor Moon was left on her own when going up against a brainwashed Mamoru and Queen Beryl.
6 Queen Nehelenia Was In Charge Of The Dead Moon Kingdom And Circus
Queen Nehelenia was the leader of the Dead Moon Kingdom and the Dead Moon Circus. Depending on the version of the anime, she wanted to stay beautiful forever and took the Dream Mirrors of others, or tried to take over the Moon Kingdom by cursing Queen Serenity. Either way, she was a strong and fearsome leader of her Dead Moon Kingdom and Circus and even managed to kidnap Sailor Mini Moon briefly. She was also impervious to most attacks, making it extremely hard for Usagi and the others to defeat her.
5 The Black Lady Was A Corrupted Chibiusa Controlled By Wiseman
The Black Lady was created when Wiseman corrupted Chibiusa after lying to her and claiming that she destroyed Crystal Tokyo in the future. This led to her being absorbed by the Evil Black Crystal and becoming the Black Lady.
Eventually, Sailor Moon managed to change Chibiusa back to normal after a few failed attempts, but the fact that even Chibiusa could become the frightening Black Lady made her a tough foe to defeat in the end.
4 Queen Beryl And Queen Metalia Merged Into Super Beryl
Queen Beryl was an extremely challenging foe from the beginning of the anime, but she got even worse when she and Queen Metalia merged to become Super Beryl. As Super Beryl, she could spread darkness around planet Earth and accelerate the sunspot activity on the sun with her mere presence alone. It took the efforts of not just Usagi, but all of the other Sailor Scouts at the time to finally take down Super Beryl for good.
3 Mistress 9, The Sovereign Of Silence, Took Over Hotaru's Body
Mistress 9, the Sovereign of Silence, took over Hotaru's body late in the Sailor Moon S arc. She had been residing inside of Hotaru's body up until then. Depending on the version of the anime, Mistress 9 either was implanted inside Hotaru similar to how a daimon was implanted in her father, Dr. Tomoe, or she took over Hotaru's body after consuming pure hearts.
If it wasn't for Hotaru managing to temporarily stall Mistress 9 late in the fight against her, Sailor Moon and the rest of the world would be toast against Mistress 9's efforts to summon Pharaoh 90 and destroy everything and everyone.
2 Sailor Galaxia Almost Destroyed The Entire Universe She Was Supposed To Save
Sailor Galaxia was introduced in the last season of the '90s anime as the strongest Sailor Scout to ever exist. She commanded the Sailor Animamates, and she sought to collect star seeds and destroy any and all worlds in the way of becoming the strongest warrior in the galaxy while under Chaos' control.
When she broke the seal of Queen Nehelenia, she forced the awakening of Sailor Saturn to have her ready for Galaxia to take all the star seeds in the solar system. She would not have done any of this if she wasn't under the control of Chaos, which she originally sealed in her body to keep the planet safe before it corrupted her. However, her being the most powerful Sailor Scout on top of her forcing the previous events of the anime to occur made her a very hard foe to defeat.
1 Chaos Itself Was The Deadliest Foe Of All
The final villain, Chaos, was the ultimate villain in the entire series. He controlled Sailor Galaxia to eliminate all human life and is the ultimate force of evil. It did not make a physical appearance in the anime, but it served as a great ultimate villain, considering how much trouble it put Usagi and her friends through in the final arc via it's control over Galaxia. Though some fans argue that Chaos' development was rushed and should have been better paced out in order to be a good final villain, it's still a powerful villain and worthy of it being the last main villain Usagi and her friends faced.