Top Ten Hardest Undertale Bosses

The Top Ten

1 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 couldn't get past the final gaster blaster circle for SO long. Weeks after my first attempt on computer (and maybe 57th) I downloaded it on my switch, and the controls are so much better. The third bone stab (where he flings you into a random wall in the box and bones try to stab you) was almost impossible to get past undamaged. And I hated constantly being hit by those final gaster blasters. His fight was by far the hardest in the game. This makes undyne the undying look like a pushover. So yeah... I ended up having a VERY bad time.

He is a really hard guy to fight, but he dose get tired after a few attacks, otherwise he's hard to kill

I think it's sans because he is a hard fight normally but if you add the poison then it's the hardest fight in undertale geez I thought it was hard enough already

I'm on like my infinity try and I still haven't beat him. I mean I use the arrow keys which is like the hardest mode in my opinion.

2 Omega Flowey

Although his battle does SAVE, no amount of skill can let you NOT DIE on this guy. To be fair, I haven't attempted the genocide route, so I haven't battled Undyne the Undying or Sans, but he is much harder than Asriel, as his battle SAVES even more.

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

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

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

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

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.

Undyne is underrated Is underrated as hell she is very strong and formidable one still unlike a filthy skeleton

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.

5 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.

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

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

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

Hard like an algebra test

6 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!"

Only person I died to in pacifist run through (and that was my first time through)

Along with Undyne, the one of three bosses I died two on my last playthrough.

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.

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

7 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.

How do people get past this sometimes first try although sans is hard I survive longer against him then undyne

Undyne is just hard no matter if its genocide undyne or regular

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.

8 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 got my vote. The way her attacks come at you. Eat a spider donut in front of her to skip the battle or if you already bought a spider donut in the ruins, in the dinner phase a spider will bring up a note and the battle will end. Struggle or pay to slow her attacks. Took me many tries.

Muffet is actually pretty easy to beat IF you saved the spider donut or spider cider. I had it and ate it in front of her. But if you don't have one, you have to spare her 17 times, I think.

No matter what I do I can't get past muffet she has a billion of spider when your running away from her "pet"

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

9 Ruins Dummy

Ok I did not vote because it's hard (we cannot be sure 'bout his gender) but because he is so easy. JUST. LET. THE. BULLETS. RUN. INTO. HIM.

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 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

Why is sans the fkrst? The dummy is a lot harder. Unless of course you're carefull not to activate him. If you do be careful for hsi God attack. And don't call for help, you'll get Toriel killed.

10 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.

The Contenders

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

Strangely I defeated Photoshop Flowey in three tries but on Tori on my second playthrough this was hard. - AlphystheDinosaur

But toriel's attacks avoid you

12 Froggit

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

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

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

Hardcore, I was stuck on them for a very long time. He wouldn't turn yellow, and I was so confused

13 Mad Dummy

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

On him rn and it is so frustrating

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

Really frustrated me on my first playthrough. - TheCrystalWolf

14 Disbelief Papyrus

I've seen videos, and tried fighting him myself...EXTREMELY HARD.

Bones orange bones blue bones orange Gaster blasts sans and Undyne the undying

Disbelief papyrus is very hard on phase 3 because he summons sans and undyne because he’s mad I think

He is just awesome that's why.

15 Annoying Dog

Hardest boss ever! Who else agrees?

Cute picture - TheCrystalWolf

Is it even a boss

best yes

16 Ultra Sans

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

Lasers hands and laser moever

He kills you if you don’t have the artifact


The blasts lol


Have you seen this dudes HEALTH?! This should be number 1! 666666666666666666666666 health!

18 Alphys NEO

Alphys have lasers Gaster blasts fast forward play raced rewind and
light nig

She's not even in Undertale! - BrokenLightbulb

The attacks cool but difficult

Harder than any boss combine

19 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

So hard. - PolishDude

Temmie for the win

HOi wElCOme tO...

Da tems to hard to beats

20 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.

Legitimately can't get rid of her in your files (unless you do some complex "hacking" stuff) so yeah

Oh jeez this has to be the hardest. Most people don't know how to battle Chara. Look it up on Youtube and watch. Most are fake actually or fan-made. Trust me, harder than Sans.

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.

So hard can't beat it

21 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

Hell to the naaw


22 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

Greatest character

23 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

24 Dusttale Sans

Seen videos and don't even wanna try cause of how he is

This dood is hecking insane, like bro.

... he has gone mentelly insane!

25 Seven Human Souls

Give me a gun. - BrokenLightbulb

26 Greater Dog
27 Mad Mew Mew

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

28 Lemon Bread

By far the hardest algamate. I died to lemon bread like 13 times the first time I fought them. I beat sans on my phone easier than this.

Very nasty first time.

Took me a few tries to beat this one

29 Final Froggit
30 Royal Guards

When you kill one the other gets stronger and if you don't know how to spare them its pretty hard

31 Vegetoid

The bouncing attacks are almost unavoidable


32 Jerry

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


HE DOESN'T EVEN ATTACK. - BrokenLightbulb

33 Knight Knight

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

Stupid annoying

Gives you hell

34 Aaron
35 Astigmatism
36 Doggo
37 Endogeny
38 Glyde
39 Lesser Dog Lesser Dog is a character from Undertale. He is part of the Snowdin Canine Unit, and is famous for his long neck.
40 Memoryhead
41 Pyrope
42 Reaper Bird
43 Shyren
44 Tsunderplane

Very prickly.

45 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.

46 Glad Dummy

Totaly easy

47 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.

The tears that go around the walls are almost undodgeable unless you spare

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

Can't kill a ghost

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

48 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

Unitale mettaton neo is harder then sans?

THEN WHY IS HE HERE? - BrokenLightbulb

49 Whimsun

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

This guy should be last. - BrokenLightbulb

50 Dogamy and Dogaressa
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