How to defeat Sans in Undertale: Complete Guide and Strategies

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If you've made it this far in your Undertale playthrough, you already know that facing Sans is arguably the most brutal challenge in the entire game. It's not a conventional fight; it's a true test of your patience and reflexes that will force you to die again and again before you see the light.

To emerge victorious, don't look for magic tricks because they don't exist. The key lies in determination and muscle memory , since you'll have to learn every movement of the skeleton almost perfectly to avoid ending up in the cemetery in record time.

The ideal healing kit for the genocide route

Before entering the courthouse, make sure you have your strongest inventory. Don't waste your potions on Undyne, as you'll need every hit point to survive Sans's frenzied attacks.

• Toriel's Cake: It is the most powerful object, because regain full healthSave it for the final stretch of the fight.
• Instant noodles: Although they normally heal little, in this fight they enter "serious mode" and restore 90 HP.
• Mettaton's Meat: A solid object that cures 60 HP and it can be purchased at the Hamburger Emporium.
• Pieces of a snowman: You can carry up to three units, and each one It will give you back 45 HP.
• Legendary Hero: They heal 40 HP. Although the attack bonus isn't very useful here, they're ideal for fill the empty spaces of your inventory.

Detailed analysis of the confrontation

Unlike other bosses, Sans has a unique mechanic: he'll die in one hit , but the problem is he won't let you hit him. It's a battle of attrition where progress depends on you managing to hit him to change his dialogue and the pace of the fight.

The encounter begins with a brutal attack designed to catch you off guard . Although shocking, with a little practice and repetition you'll be able to dodge it almost unscathed, making it just another routine part of the battle.

Combat phases and attack patterns

In the first stage, you'll face a mix of bones and Gaster Blasters. The key here is to memorize the routes , especially in platforming attacks where the path is fixed and traps always appear in the same place.

There will come a time when Sans will offer you peace. This is the perfect moment to fully heal yourself without fear of the fight progressing, as the battle won't continue until you decide to attack. However, don't use your strongest items unless absolutely necessary.

The second phase is where things get ugly. Sans will start using combos of chained attacks that will test your reaction time. You'll see Gaster Blasters firing from all directions and the dreaded telekinesis, which throws you against walls. One trick people are talking about is pressing all the arrow keys at once during the shoves to minimize the damage.

One of the trickiest parts is the bones that move up and down simultaneously. The best strategy is to stay in the center and make small, constant circles to take advantage of the gaps.

Interface traps and the final attack

Sans doesn't play fair and will bring danger right into the combat menu. You'll see bones sliding across the action buttons. To avoid damage while selecting an item or attacking, you must act coolly and confirm your actions quickly , coordinating your movements with the bones' movement.

Before closing, it will unleash a devastating sequence: telekinesis, ascending bones, a high-speed dash, and finally, a circle of Gaster Blasters . To survive this last attack, position yourself in the bottom right corner towards the center and rotate in time with the blasts.

The outcome and the final blow

When Sans gets tired, you'll enter the final phase. The skeleton will decide to do nothing to avoid it being your turn. However, exhaustion will take its toll, and he'll fall asleep . At that moment, you must move the soul to the left to push the combat box until you reach the fight button.

Although Sans will dodge the first attempt, he will receive a second devastating blow that he will not see coming, ending his resistance and completing the feat.

If you feel stuck, there are tools like the Bad Time Simulator , a web-based recreation of the combat that lets you practice specific attacks on a loop. It's an excellent way to hone your reflexes without having to repeat the entire walk to the courthouse. Once you've mastered the patterns and optimized your use of healing items, you'll be able to overcome this difficulty hurdle and defeat Undertale's most iconic boss.