Top 10 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 die to the first attack every time. I only got past the first attack once, I only got to the seventh attack, and then died on the next

It took me over a 100 times just to beat a lazy-funny skeleton who Actually can kill you without even fighting it's just insane oh yea now your jumping over bones which he does it pretty fast oh, great now blue then white bones its just crazy when your done halfway it just gets crazier your being thrown with force very fight with bones appearing in the red box which is very hard if u lose control, and u have to dodge all the gaster blasters SOMEHOW and then the final attack going threw a wave of bones then ALL THE FREAKING BLASTERS U HAVE TO RUN AWAY FROM THEN HE THROWS YOU EVERYWHERE until when u kill him... it's also the 1. saddest death. he says "Papyrus do u want anything" and u feel really bad now. :'(

Sans is by far strongest, let’s not forget he is the one that attempts to get revenge for his brother and friends. He may be a bit lazy, but his terrific humor is too funny to be bad. Anyways, Sans is the strongest despite his low hp.

I've died probably over 100 times at the point and I'm not getting anywhere close to beating him. My personal ranking is: #1 (by far) Sans, #2 Undyne the Undying (probably died over 15 times), #3 Omega Flowey beat him in one attempt on my first playthrough and only died once on my second.

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

Omega flowey (or photoshop flowey) is, in my opinion the hardest, as it’s much harder to remember the attacks and honestly, he is actually terrifying

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.

Looks like the hardest boss ever (tied with sans) because it's so powerful imagine a talking attracting deadly flies swinging cactus hands and shooting barrages of seeds all at once. Well good luck on that one because its pretty damn hard

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

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.

It took me 3-4 tries to get used to there attacks but after that they were quite easy to beat

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

Sans may be the strongest but he can't even beat asgore nor asriel since sans is the almost main character dosen't mean he's the strongest

4 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.

One of the hardest bosses. Worn dagger is the strongest in this route but burnt pan is the best. It can do 300 or more damage with perfect hit.

I'm stuck to the pacifist checklist, and have no healing so he's impossibly difficult.

Asgore took me a while to beat but after that, I got his attacks in my head easier.

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

5 Undyne The Undying 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.

Undyne The Undying is so strong because of her Determination to protect the whole world in the genocide routeand is confirmed to have Determination she will melt when she tries to do this in the neutral route.

Undertale is a flawless game besides the fact that Toby wanted the 2 bosses of the genocide run to be hard and not so fun. But I think that some parts of the undyne fight are pretty fun pretty good boss. But why is she at 5, she should be at least 2 maybe even 1

I beat every boss in undertale within 4 or 5 tries. This is all except for undyne the undying (who I have been stuck on for weeks) and sans (who I haven't fought because I'm stuck on undyne the undying). Omega flowey took me about 3 tries, and was a really quick boss fight because I'm pretty sure you don't have to repeat phases. Asriel shouldn't be on this list because you can't die to him. Asgore was the hardest boss in all of the neutral/pacifist route (took me 5 tries), however he does not even compare to the difficulty of undyne the undying. She should be second on this list.

She was so annoying to beat her green heart attack things were easy enough but I died a lot on the red heart parts because they were really hard to douge

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!"

HARD you have to dodge all his attacks ALSO have to get hit to raise the like preformance thing above 6,000 to get rid of his arms then it becomes a little more easy

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.

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

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.

Waterfall is peaceful without Undyne and Mad Dummy. It should be noted there's a way to skip a part of the battle if you get low hp, or even better if you use a skip with healing item. This skip is not a glitch, by the way.

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.

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

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 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

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.

like mettaton you have to survive past her "pets" breakfast,lunch,dinner then desert then one of the spiders tell her it was a mistake that there was another person with a striped shirt (probably chara but who knws) then he lets you pass

9 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.

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

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

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

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

10 Toriel

Technically, you can't die in this fight, but just TRY to not get to 2 HP when you are on pacifist. It's freaking impossible!

No... Toriel is not the hardest boss, his the easiest boss just click spare do nothing

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

But toriel's attacks avoid you

The Contenders
11 Mad Dummy

Waterfall is peaceful without Mad Dummy and Undyne. There's a way to win this in five turns but this requires certain moves on the enemy turn.

Took me many tries. I just couldn't lead the projectiles to the dummy without getting hit myself...

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

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

I'm out of knives.

12 Disbelief Papyrus

this papyrus is so hard that the first attack brings you done to 1 hp and the fact that he can block in phase 1, reflect in phase 2 and keep you from using items, and the fact in phase 3 he summons undyne and sans

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

He is way stronger than regular papyrus

*Papyrus no longer believes in you

13 Froggit

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

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

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

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


I mean... I like his lore.

He made the op sans

The blasts lol

W.D gaster is almos impossable to beat. 1 he can crash your game. 2 his attacks are hard to dodge and 3 he can't be spared or killed

15 Annoying Dog

This is actually mist likely the strongest character in the game, he created this world (undertake), so he can easily destroy it all, he could kill you (Frisk),Sans, Papyrus, Undyne, just with a single button

By Derpo

Hardest boss ever! Who else agrees?

Is it even a boss


16 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.

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.

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

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

At the end, you end up dying from her

17 Ultra Sans

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

The strongest sans

Lasers hands and laser moever

He kills you if you don’t have the artifact

18 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.

Da tems to hard to beats

Temmie for the win

HOi wElCOme tO...

TEMMIE: HOi I'm TeMMi (temmie is trying to glomp you)
FRISK: >:(


19 Frisk

You control Frisk, so you can't kill her. Maybe in fan-games, but not Undertale.

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

I lke chocolate

20 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!

Yeah also the omega flowey is insaneley hard

This dude sssoo easy

Hell to the naaw

21 Dusttale Sans

He has fReAkInG more Determination than you in the fan-game.

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

I tried but I wasn't good so I died very quickly

;-; I don't know why did I vote for him

22 Alphys NEO

The attacks cool but difficult

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

Harder than any boss combine

She's not even in Undertale!

23 Greater Dog

This is easy all of the attacks just barking when you just used ACT (in pacifist run) I don't know what happens if we do a GENOCIDE RUN. maybe you should try it!.

Honestly I was stuck on this for so ages my 1st run. I was trying pacifist but gave up and went neutral.

24 So Sorry

I feel so sorry for so sorry. He doesn't mean to fight you. He just ran into you and started the fight

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

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

I don't know who he is

25 Mad Mew Mew

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

not that hard second time through

probably low because switch exclusive BUT HARD

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