Undertale: The Genocide Route’s Final Boss Guide

This guide is aimed to teach you how to not suffer as much. You’ll still suffer probably. Spoiler Alert!!!



Chances are you are being murdered over and over again. How fun. If you’d like to turn the tables however, you’ll have to have some info.

To start it off, a Youtube video that helped me a bit when I had the same problem as you.

This video will give you some tips. (obviously)

Important Tips / Basic Tips

We’ll start off with the most important tip: Stay determined! It took me about a month or two to beat this final boss when I first played, but now I can beat it without much trouble. And I only beat it because I didn’t give up. If you give up easily, then you’re gonna have a bad time.

However, there is also another thing you need to know: Take breaks! I tend to do better on hard challenges when I haven’t failed them 50 times in a row. The more tired you are, the more likely you’re gonna fail. If you’ve died over and over, do other things for a bit, like:

  • Read a book
  • Do nothing
  • Go to sleep
  • Pet a dog
  • Pet another dog
  • Realize you don’t have a dog
  • Pet a dog
  • Pet the 2nd dog
  • Pet the 4th dog
  • Wonder where the 3rd one went
  • Pet a dog

Now, yet another important tip: P R A C T I C E. When I first played, I spent a bit too much time looking for tips that I already knew. I only won when I was getting practice from fighting him. Chances are, you may be doing the same thing! However, getting tips is definitely not a bad thing. Just remember to practice too.

(If you want more tips, go to the Extra Tips section)

That’s enough talking for these tips, now we should move on to the attacks and strategies!

1st Phase

The first phase isn’t too bad, but it can still do quite a bit of damage if you don’t know his patterns.
His first attack is supposed to catch you by surprise, and definitely does. With a bit of practice, however, you can no hit the first attack with ease. A general tip is to only move up and down to dodge all of it, as moving left or right rapidly can confuse you. Another thing to mention, don’t hold jump at the start or you’ll take a bit of damage. Practice is key.
(1.) After that, do the tiny bone jump attack by pressing UP only and not holding it.
(2.)After that, the blue bone attack is simple. Jump to the left, stand still, repeat, until the attack switches positions and jump to the right instead of left.
(3.)The third attack is just the bone jumps, but more random. Know what you’re doing and you’ll be fine.
(4.)Here comes the platforms. Be careful, do NOT fall off or you’re gonna either die or lose at least half of your health. These attacks generally have tricks, yet again know what the attack is and you’re fine.
(5.) Still platforms. The second platform can be entirely skipped, and some platforms don’t require you to jump (if you do you’ll get stabbed by an above bone) in order to avoid it. A no-hit video would also be helpful.
(6.) Stay still until a bone comes near you. Jump over its platform, and repeat.
(7.) Jump through (or stay still and time it) the bones when your platform goes through them. At the last jump, don’t go through it and instead do a full power jump and stay still. After that, the attack ends.
(8.) Stay still until a blaster forces you to jump. Pretty similar to 6.
(9.) Same as 7 but faster and harder. Same tips.
(10.) Same as 1 but a lot faster.
(11.) Hug the right wall until you need to time your jump, jump, don’t land on a bone, and then repeat.
(12.) Same as 3.
(13.) You did it! He’s tired. Heal up, he won’t attack and you can use as many items as you want. After that, attack and be prepared for the 2nd phase.

2nd Phase

Things get harder from here. And by that, I mean much harder. If you thought phase 1 was like challenging Hades to a fist fight, in the words of that Deltarune secret boss:
“Bye bye!”
This phase requires mostly excellent reaction time, and tips start to become less important and skill becomes even more important.
(1.) Dodge each attack that’s coming for you. There’s too many to give a detailed description, just make sure you don’t get too confused and walk into every bone he can throw. Have at least somewhat of an idea on how to dodge all of the attacks.
(Your turn. Yes. I’m not kidding.) He’s attacking during your turn now. Timing is key, yet again. Note that this bone cannot kill you, nor deal Karma damage, but it’ll hurt. A lot.
(2.) Everybody’s 2nd favorite attack: Blaster spam! Mostly just move everywhere, you have a lot of room to dodge. There’s also, everybody’s 1st favorite attack, Big Mac Blaster Spam™. Be prepared for it later.
(Your turn attack 2. Yes. He makes his own rules.) Bones appear and attack you at the bottom. Soon enough you’ll have both of the “your turn” attacks at the same time. Don’t stand still otherwise you’ll get stabbed.
(3.) Same as 2nd Phase attack 1, but with different patterns n’ blasters. Same tips, know what you’re doing, don’t die.
(4.) Blue soul throwing. It gets a lot faster later, but for now it’s easy.
Pro Tip: If your reaction timing is on vacation (permanently), you can hold all of the movement keys. You may take some damage, but it’s a lot better than staying still and dying.
(5.) Guess what? 4 but faster. He REALLY likes making his attacks faster and nothing else, huh.
(Your turn attack… 3… why.) Both “your turn” attacks at the same time. Only safe place is the non-first items.
(6.) Big Mac Blaster Spam™. A bit easier to see the blasters, a bit easier to see your SOUL being shot to death. Same tips as 2.
(7.) Bones following gravity, other bones not following gravity. Pretty much: s p i n. Not much else to explain
(8.) If your reaction time is on vacation, your life is on vacation. Number 1 but pain. Not much to explain.
(Hey, I rhymed! =D)
(9.) The final version of number 4. He actually uses that sort of attack like 6 times, and even more in different styles. He REALLY likes yeeting you into the walls, ceiling, and floor.
(10. The FINAL Attack.) Heal up. HEAL. UP. I’ll split this into multiple parts.(10 A.) He slams you into the walls with bones, same speed as number 9, and then uses number 7.
They are all just shorter versions of that attack, same tips.
(10 B.) Once again, yeeted into the abyss. Sad. Messing up at this attack gets you killed. Similar to the attack used in the multi-attack and the 1st attack, but longer. Move up and down when required. After that, the bone blocks require you to move up and down rapidly. Not moving far enough will hurt you, and moving too far will also hurt you.
(10 C.) Similar to the first move of 10 B. Stay in the middle of the box and you’ll be fine. After that, avoid the bone trick at the end by jumping left.
(10 D.) Pattern bone jumps. Also, they require you to move diagonally sometimes. Move in this pattern:
Up to the ceiling, Down to the bottom right corner, Up to the top left corner, Right, and finally…
(Attack E.) BLASTER SPAM: NEW AND IMPROVED. Yeah. Messing up will end you.
Move around in circles for your life. Don’t go too far away from the center, orrr… you’re dead. Don’t go directly IN the center, or you’re dead. Stay around it, and move away from the blasters. Don’t get stressed, too, as that will effect it a lot. Stay calm. If you do it well enough, you did it! Deal with the special attack, kill em, and boom. You now have completed the game.

Advanced/Extra Tips

Now, you’re still probably in pain, even with those tips. If you want even more, I can help with that.

First of all, there is a website known as Bad Time Simulator.(https://jcw87.github.io/c2-sans-fight/ )This is a recreation of the Sans fight, and can help you with practice. There is an option to repeat certain attacks, which can help if you have trouble with a certain one. There is also a “Practice” mode that helps you too.

Second, videos, A lot. More specifically, tutorials and no-hits (Or, alternatively, no items). A no-hit means that they got through a specific part of the game without taking damage (Unavoidable damage does not count, for example, this boss’s final wall slamming). These can help you by showing what you need to do in order to survive.

A good No-Hit video is here:

Third, speed things up by spamming X and Enter/Z when he talks, and don’t aim for the strongest point when attacking. These things can make the battle much shorter. Also, pay attention to his text before he’s about to use his “Special attack”, so you can be prepared and not have to deal with the final attack at 1 HP.

By User01

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