Top Ten Hardest Undertale Bosses


The Top Ten

1 Sans Sans Sans or Sans the Skeleton is a character in the 2015 RPG Undertale created by Toby Fox. He is a lazy, pun-loving skeleton who is a supporting protagonist in the "pacifist" and "neutral" routes of Undertale, and a heroic antagonist/final boss of the "genocide" route. He is known for his incredibly difficult more.

For those who are struggling on the gaster blaster attack, pay attention to the most recent blaster - Pokemonfan10

You need to beat really hard things before you fight Sans, and Sans is harder than those.

REALLY? Come on, Sans is SUPER EASY, and I'm not even good at Undertale. He was a disappointing final boss, and I beat him in like 3 tries.

He really can be hard depending on when you fight him.

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2 Omega Flowey

I had no idea what I was doing with Photoshop Flowey, yet somehow I survived.
Until Finale. I was doing just fine. Then when the fight got easier, I died. I'm so good at this. - TheCrystalWolf

I like omega flowey

It is so hard because surivicing and fight him the same time.

very hard

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3 Asriel Dreemurr Asriel Dreemurr Asriel Dreemurr is a character from the 2015 game "Undertale". He was created by Toby Fox. more.

Didn't want to vote for this, but you cannot die during this fight. Froggit is easier

You can die but in asriel's first attack if you die you go 2 attacks back so for asriel's first form you have to live. In his true form, however, id you die it doesn't matter.

But guys, try beating Asriel without even supposedly dying, you'll see he is DAMN HARD

You do lose battle progress when you die. Or, when you undie. - TheCrystalWolf

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4 Asgore Asgore Asgore Dreemurr is a boss monster and the king of the monsters in the 2015 RPG Undertale made by Toby Fox. Asgore is the portrayed main antagonist who plans to acquire seven human souls and use their power to break the barrier that seals the monsters underground . Aspects of his character are hinted more.

Asgore is like an exam you didn't study for. - TheCrystalWolf

The only boss that I died to more than 1 time (Not counting Papyrus)

I beat Asgore first try, Muffet and Undyne were pretty hard though

Asgore is stronger than omega flowey I lost to asgore 20 times but I beat omega flowey easy

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5 Undyne The Undying

100% undyne. Just impossible. I have no idea what Toby fox was thinking, adding them to the game. Not even a psychopathic murderer would deserve this fight. But still, my favorite boss fight in undertale.

100% the 2nd most difficult boss fight. Took me at least 25-40 tries to beat

I got past Undyne the Undying, and it only took me 480,900,4321 tries! - TheCrystalWolf

Undyne the undying should be in 2nd place after Sans!

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6 Mettaton Mettaton Mettaton is a character in the popular 2015 RPG game, Undertale. He is a robot with a soul built by Dr. Alphys, and is the sole television star of the underground. Mettaton is a popular character in the fanbase. His notable features include his legs, and his catchphrase "OH YESSSS!"


Spam Boast and I'm not kidding it's easy after that.

The background music is good but he is challenging as hell!


7 Undyne Undyne Undyne is a main character in Toby Fox's 2016 RPG, Undertale. She is the heroic fishlike captain of the Royal Guard, who takes it upon herself to protect the monsters of the Underground. Her name is derived from the word "Undine", and is a pun on the word "Undying". Her most loved monsters are her mentor, more.

The only way to spare her is running away until your red and then run to the hotland bridge, let her faint, then give her water.

This is way harder than any of the above apart from sans.

I don’t understand how some people get through this so easily.

Here's a little fun fact: I died to Undyne more than I did to Photoshop Flowey, Asriel Dreemur and Asgore combined. The NORMAL Undyne, not Undyne the Undying. WHY ME - Mewtwo660

8 Muffet Muffet Muffet is a character from the game Undertale. She appears in a region called Hotland, selling pastries to raise money to rent a heated limo to help the spider clan from the Ruins (who are also raising a bake sale) reunite with the one in Hotland because the spiders can't cross Snowdin.

Just drink spider cider

I wouldn't know because I always used the Temmie Armor. - TheCrystalWolf

Took 3 days. I asked my dad to try. He beat it first try. What the heck?

Still stuck here

V 2 Comments
9 Papyrus Papyrus Papyrus is a character from the 2015 game Undertale, made by Toby Fox. He is the Younger brother of Sans the skeleton, royal guard in training, and a sentry in the town of Snowdin. Opposite to his brother, papyrus is active, loud, and full of himself; but in an endearing way. Papyrus means to become more.

Papyrus is pretty easy if you ask him on a date then he gets really distracted

No...Papyrus is easy...Plus you can skip his battle and befriend him if you die three times instead.. - SansySenpai

He was only threatening in Disbelief. In regular Undertale, he is a cake walk. - TopTenX

I don't think you can actually die against him - it's impossible.

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10 Ruins Dummy

I tried so many times to get past it, but it was too hard. Eventually, I had to hack my game. What was Toby thinking? Putting a battle like that in the game? - TheCrystalWolf

Lol m8 so hard watch out for his god attack

Watch out for his dual weilding assault rifles attack. Each bullet can kill you in one shot, even with max health with max LV. Had to get my russian hacker comrade to hack the game to help me beat him.

I find it ironic that Ruins Dummy is on the list but Mad Dummy isn't.

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The Newcomers

? Dusttale Sans

This dood is hecking insane, like bro.

The Contenders

11 Toriel Toriel Toriel is a main character in Toby Fox's 2016 RPG, Undertale. She is an amazing blend of goat and mother.

But toriel's attacks avoid you

12 Froggit

Froggit didn't understand what you said, but was flattered anyways. - TheCrystalWolf

Yes iam joking


Just a normal froggit, but it took me 26 trys and this froggit, is a hacker, or am I gliched?

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13 Mad Dummy

Really frustrated me on my first playthrough. - TheCrystalWolf

I don't need friends! I've got knives!

i'm out of knives.

On him rn and it is so frustrating

14 Annoying Dog Annoying Dog

Cute picture - TheCrystalWolf

Hardest boss ever! Who else agrees?

15 Ultra Sans

He is awesome and he is so hard if you think sans is hard try this dude

He kills you if you don’t have the artifact

16 Mettaton NEO Mettaton NEO

Harder than Getting Over It - Pokemonfan10

THEN WHY IS HE HERE? - BrokenLightbulb

SO EASY - coolgamert

17 Alphys NEO

Harder than any boss combine

She's not even in Undertale! - BrokenLightbulb

18 Temmie Temmie Temmie is minor character from the 2015 game Undertale made by Toby Fox. Made in the likeness of her artist, Temmie Chang, in appearance and character. Both a character and a species of monster, temmies are defined by their mix of cat and dog features, as well as their broken English. Their hidden village more.

Temmie for the win

HOi wElCOme tO...

TEMMIE for the win

So hard. - PolishDude

HoI I'm TeM wELcomE To TEm shOP

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19 Seven Human Souls

Give me a gun. - BrokenLightbulb

20 Greater Dog Greater Dog
21 Chara Chara Chara is a character in the game Undertale by Toby "Radiation" Fox who is one of the seven people to fall to the Underground prior to the fall of the player character. Her name can be changed by the player and will be assumed as the player character, until the Pacifist Route when Asriel asks for the more.

So hard can't beat it

So hard why down here

Chara is a god. She can kill you so quick.

Hey, I have a Au that Chara is a monster, lol. SHE IS SUUPPEEERR HARD PEOPLE. THINKING OF MAKING A GUIDE TO HELP. Anyway, MonsterTale ( that's my au) Chara is super hard to stop.

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22 So Sorry

This is a secret boss, but it's hard, I can say it's the sixth hardest boss after ASGORE

Harder than undyne, muffet and maybe mettaton

23 Goku Goku Son Goku (Kakarrot) is the main protagonist in Dragon Ball franchise created by Akira Toriyama in 1984. He has many abilities like, super strength, utilization of ki, flight, teleportation, super speed, enhanced reflexes, and Super Saiyan transformation that increase strength, speed, and durability. more.

Definitely an undertale boss...

I'm do so awesome



25 Mad Mew Mew

I wouldn't know. I played on a computer. - TheCrystalWolf

26 Disbelief Papyrus Disbelief Papyrus
27 Napstablook Napstablook Napstablook is a secondary character from Toby Fox's 2016 RPG, Undertale. He is the cousin of Mettaton, who left him in order to become famous. Due to this, poor Blooky has crippling depression.

Missed the memo and is the same difficulty as before. - TheCrystalWolf

Can't kill a ghost

Don't cheer his dapperblook...I DARE YOU

28 Lemon Bread

Very nasty first time.

Took me a few tries to beat this one

29 Jerry

I like how ditching Jerry is an option. Just ditch him a couple of times


HE DOESN'T EVEN ATTACK. - BrokenLightbulb

30 Knight Knight

It was easy for me, because I learned Shyren's song by humming five times. - TheCrystalWolf

Stupid annoying

Gives you hell

31 Aaron
32 Astigmatism
33 Final Froggit
34 Memoryhead Memoryhead
35 Royal Guards
36 Shyren
37 Flower Flower Flowey is a flower in the RPG Undertale. He is the first character you meet, and also your best friend.

This dude sssoo easy

38 Snowdrake's Mother Snowdrake's Mother

Snowdrake's Mother is well, Snowdrake's Mother, as well as Snowdrake's Father's wife and an, amalgamate found in the True Lab. It is fused with 16 monsters. It's battle music is a slowed, distorted version of the Snowdin Forest Music. It can morph from a refrigerator to something man-shaped to the image found in the infobox.

39 Whimsun

Halfway through your first word, Whimsun bursts into tears and runs away. - TheCrystalWolf

This guy should be last. - BrokenLightbulb

40 Doggo
41 Dogamy and Dogaressa
42 Endogeny Endogeny
43 Glyde
44 Lesser Dog Lesser Dog Lesser Dog is a character from Undertale. He is part of the Snowdin Canine Unit, and is famous for his long neck.
45 Moldsmal
46 Pyrope
47 Reaper Bird Reaper Bird
48 Tsunderplane

Very prickly.

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List Stats

800 votes
49 listings
2 years, 309 days old

Top Remixes (4)

1. Sans
2. Undyne The Undying
3. Omega Flowey
1. Sans
2. Undyne
3. Omega Flowey
1. Asriel Dreemurr
2. Sans
3. Omega Flowey

View All 4

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