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.

I think Sans is pretty easily the hardest because of many reasons such as, his attacks at the start are unexpected and will add a quick few deaths to the amount you will have through this fight, players will get annoyed eventually and when people are annoyed they play worse, Sans irritates the player by dodging their knife swings, Sans final attack is very hard to dodge, all of Sans attacks involve parkour dodging and swift movements and also within sans fight you spend a lot of the fight with the blue heart which is harder then the red heart. Those are my reasons why sans fight is the hardest and by the way I’m sorry this comment is very long I just wanted to point out a lot of reasons thank you for reading!

Undertale, the game that has the weakest character be the most powerful character.

His last Attack is Chaos

He is so hard guys

2 Omega Flowey

Other boses are challenging but you can memorize there attack patterns over many repeats you can do that with flowey sure but I don't have the reflexes. I remember coming out of the asgore fight and found him one of the easiest bosses but then flowey came and killed me almost instantly over and over I haven't fought sans or Asriel but I can't see them coming close to the difficulty of flow since I can't fight him for more then 20 seconds

I say omega/photoshop flowey is the hardest... He throws all his attacks at once! But... Asriel posseses flowey then... How does he have 2 forms?!?!
Wait... Actually 3
But still!

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

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

Super hard boss

Only boss I died to. (not counting sans or omega flowey.) LIKE, COME ON. IN HIS TRUE FORM, HIS ATTACKS ARE INSANE. But the sad part is... when... he begs for you to let him win. Then he does that INSANE attacks where you barely survive.


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

4 Undyne The Undying

Out of all the bosses I've fought so far, Undyne The Undying takes my vote. Bear in mind that since I haven't been able to get past her yet, I haven't fought Sans or any bosses that only appear in Genocide past Undyne The Undying, but she is easily the hardest so far.

Why is this only 4#?! This is the SECOND hardest boss I have done! Asriel is the easiest! You CANNOT DIE IN THAT FIGHT!

It took me about 70 tries to finally beat her. I was about to reset because of her. Sure, Sans is EXTREMELY hard... But Undyne takes my vote.

Easily the hardest - ListerBlister

5 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

Actually, the fight is not that hard of you eat the pie.

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!"

Died a few time

Found him harder then asgore

So hard to not die on pacifist, so annoying!

Mettaton is the hardest pacifist fight, in my opinion. His attacks are super chaotic, and almost impossible to dodge. Some may say Asgore is harder, but once you get his attacks he's super easy. It took me 8 items to beat Mettaton and only 5 for Asgore. I died 3 times for both but barely beat Mettaton with 2 health whereas beat Asgore handily. The reason why Mettaton is harder than Flowey or Asriel is because you can't lose to them. Anyway, Mettaton is epic.

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.

Muffet is my fave character and super evil and cute. I mean, she can also control your soul like Sans and every time I see the doughnuts and pastries I get hungrier which breaks my concentration

Its just so annoying how the pet is impossible to escape from! It took me like 15 tries to beat her... on my genocide run!

Muffed is so hard imma ask my brother to do her for me bin stuck on her for weeks

I went back to waterfall and got like so many sea teas

9 Ruins Dummy

Everything was a piece of cake until this fight. Took me SO LONG to get past it. Also, beware it's last attack. Those bullets are insta-kills!
What the heck, Toby!
And this site! How is this number 6?! It's worse than Sans!

i stopped playing cause I couldn't defeat him

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

10 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.

1 Comment

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

Hardest boss in game. don't even tell me anything else you fool!

You better be joking!

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

Yes iam joking

13 Mad Dummy

He took me around 4 or 5 tries to beat, so not really that hard... - SansySenpai

Attacks get me sometimes(especially on dummy bot final).

Really frustrated me on my first playthrough. - TheCrystalWolf

On him rn and it is so frustrating

1 Comment
14 Annoying Dog Annoying Dog

Is it even a boss

Cute picture - TheCrystalWolf

Hardest boss ever! Who else agrees?

15 Mettaton NEO Mettaton NEO

She is my Favorite Character never battled her before I just started I know about it from Videos REALLY Cool

Harder than Getting Over It - Pokemonfan10

1 hit death

THEN WHY IS HE HERE? - BrokenLightbulb

1 Comment
16 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

17 Alphys NEO

Harder than any boss combine

She's not even in Undertale! - BrokenLightbulb

18 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.

I can’t beat Chara

19 So Sorry

Harder then muffet, undyne, papyrus and maybe asgore but not mettaton

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

20 Disbelief Papyrus Disbelief Papyrus
21 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

22 Seven Human Souls

Give me a gun. - BrokenLightbulb

23 Greater Dog Greater Dog
24 Frisk Frisk

Frisk is easy to beat. Just get her soul to run into something harmful.

Frisk is easily the hardest boss in the entire game, you can’t even hit them. Why did Toby Fox put an unbeatable boss in the game smh

25 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

He's really easy but it's hard not to get distracted by dapperblook ^°^ adorable



27 Mad Mew Mew

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

28 Final Froggit
29 Flower Flower Flowey is a flower in the RPG Undertale. He is the first character you meet, and also your best friend.

He almost instakills you with a single hit, manipulates you and makes it impossible to escape. By sheer luck they make a mistake and use a super heal on you which they could use on themselves easily! Also don't even have the option to act! They just have one attack and they go first instead of you plus they will remember everything!

This dude sssoo easy

30 Lemon Bread

Very nasty first time.

Took me a few tries to beat this one

31 Jerry

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


HE DOESN'T EVEN ATTACK. - BrokenLightbulb

32 Knight Knight

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

Stupid annoying

Gives you hell

33 Aaron
34 Astigmatism
35 Doggo
36 Endogeny Endogeny
37 Memoryhead Memoryhead
38 Pyrope
39 Reaper Bird Reaper Bird
40 Royal Guards
41 Shyren
42 Tsunderplane

Very prickly.

43 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.

44 Dusttale Sans

This dood is hecking insane, like bro.

45 Vegetoid


46 Whimsun

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

This guy should be last. - BrokenLightbulb

47 Dogamy and Dogaressa
48 Glyde
49 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.
50 Moldsmal
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List Stats

1,000 votes
51 listings
3 years, 94 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

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