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How to Achieve a Perfect Pacifist Run in Undertale

Achieving a True Pacifist ending in Undertale requires more than just sparing every monster. It demands a deep understanding of the game’s mechanics, character interactions, and hidden triggers. The core principle is simple: never kill anyone. But the devil, as they say, is in the details. To achieve a perfect Pacifist run, you must defeat every boss encounter non-lethally by using specific ACT options, befriend key characters, and complete a specific set of post-game quests before facing Asgore and Flowey. This guide provides a comprehensive roadmap to navigate the Underground with unwavering mercy and unlock the game’s most rewarding conclusion.

The Road to True Pacifism: A Step-by-Step Guide

A successful Pacifist run hinges on carefully chosen actions throughout your adventure. Here’s a breakdown of what you need to do in each area:

1. The Ruins

Toriel: Show her mercy after reducing her health. Keep using the “Spare” option until it becomes available. Exhausting other ACT options first, like “Talk,” can help.
Froggit, Whimsun, Moldric: Spare them immediately. Use ACT options like “Compliment” or “Threaten” on Froggit to make them easier to spare.

2. Snowdin

Snowdrake: Use the “Joke” option until he doesn’t want to hear your jokes anymore, then “Spare” him.
Doggo, Dogamy & Dogaressa, Greater Dog: Use the “Pet” and “Roll Around” options for Doggo. For Dogamy & Dogaressa, use “Re-sniff” until they are happy, then “Spare” them. For Greater Dog, use “Pet,” “Play,” and then “Spare.” Unequip any armor to show weakness, which makes him easier to spare.
Papyrus: This is a crucial battle. Lose the fight. You cannot defeat Papyrus. He will eventually tire and offer mercy. Accept it! You must also date Papyrus after your initial encounter. Go to his house, and accept his date.

3. Waterfall

Aaron & Woshua: Flex for Aaron and use Clean for Woshua, then spare them.
Shyren: “Hum”. Then choose “Hum” again if the battle continues, or talk to Shyren and encourage her.
Undyne: This is another key battle. Do NOT attack Undyne. Instead, Flee every turn until you reach Hotland. Keep fleeing even after she chases you. Once in Hotland, she will collapse from the heat. Give her water from the cooler near the bridge. After this, befriend Undyne. Go to her house in Waterfall, and choose to “fight” her.

4. Hotland & Core

Muffet: The Spider Dance encounter. Eat a Spider Donut or Spider Cider during the fight (bought from the Ruins spider bake sale). She’ll receive a telegram, and the fight will end peacefully.
Mettaton:
- Mettaton EX: Increase the ratings to 10,000. Use ACT options like “Pose” and “Boast”. Switch to “Shoot” when he exposes his heart.
Mad Dummy: Pacifying Mad Dummy in Waterfall is essential. Use the “Talk” ACT to attempt talking him down.

5. New Home

No enemy encounters here.
Proceed directly to Asgore.

6. Post-Asgore

Do NOT fight Asgore. Flowey will intervene.
Defeat Flowey by surviving his attacks.
After Flowey is defeated, befriend Undyne and Alphys.
- Undyne: If you haven’t befriended her already, go to her house in Waterfall after defeating Flowey. After receiving the letter to Alphys, deliver it to her laboratory.
- Alphys: After delivering the letter, you’ll start a date with Alphys at the MTT Resort. Follow Undyne’s and Alphys’s instructions, and be honest with your feelings. After the date, Undyne will mention something she forgot to do and will run ahead, you need to follow her and Alphys into Alphys’s True Lab.

7. The True Lab

Navigate the True Lab and learn about the history of Flowey and the Amalgamates.
This area involves no fighting; simply explore and interact with the environment.

8. The Final Battle: Asriel Dreemurr

After the True Lab, return to Asgore’s castle.
This time, Papyrus, Undyne, Alphys, and Sans will interrupt the battle.
You will face Asriel Dreemurr.
During the first phase, simply “Struggle.”
During the second phase, “Save” your lost friends.
Console Asriel.
Congratulations! You’ve achieved the True Pacifist ending!

Frequently Asked Questions (FAQs)

1. What happens if I accidentally kill a monster?

A single kill will lock you out of the True Pacifist ending. You’ll need to reset your game and start over. However, you can still achieve the Neutral Ending by sparing all the other monsters.

2. Do I have to spare every single monster encounter?

Yes, you must spare every single enemy in every encounter. Random encounters are often essential to spare.

3. Is it okay to use items to heal?

Yes, using items to heal is perfectly fine and necessary for survival. Healing doesn’t violate the Pacifist rules.

4. How do I know if I’m on the right track for a Pacifist run?

Pay attention to the dialogue and actions of the characters. Papyrus will express happiness at your friendship, Undyne will soften after your “fight”, and Alphys will eventually open up to you. Also, after defeating Flowey and loading your save file, Papyrus will call you and the real true pacifist quest line begins.

5. What if I can’t seem to spare a particular monster?

Experiment with different ACT options. Each monster has specific actions that make them vulnerable to sparing. Consult online resources if you’re struggling with a particular encounter.

6. Do I need to fight Asgore at all?

No, you will not fight Asgore in the True Pacifist ending. Flowey interrupts the battle.

7. What’s the purpose of the True Lab?

The True Lab provides crucial backstory about Alphys’s experiments with determination and the creation of Flowey and the Amalgamates. It’s essential for understanding the lore and unlocking the True Pacifist ending.

8. Can I complete a Pacifist run on my first playthrough?

It’s highly unlikely. The True Pacifist ending requires knowledge of the game’s hidden triggers and character relationships. Most players achieve it on their second or third playthrough.

9. How do I befriend Papyrus?

Simply do not attack him during the fight, spare him, and go on a “date” with him at his house.

10. How do I befriend Undyne?

You must flee from her during her battle in Waterfall. Then give her water when she collapses in Hotland and then visit her house to fight her. You must pretend to date her in order to fully befriend her.

11. What happens if I kill Flowey at the end of the Neutral Run?

Killing Flowey in a Neutral Run prevents you from triggering the True Pacifist ending immediately. You’ll need to reset and play through the game again, ensuring you befriend Undyne and Alphys before your final encounter with Asgore.

12. Does my LOVE (Level of Violence) stat matter in a Pacifist run?

Yes, your LOVE stat must remain at 1 throughout the entire game. This is because LV increases with killing and represents how desensitized you become to violence.

13. What’s the difference between a Neutral ending and a True Pacifist ending?

A Neutral ending is any ending you get after beating Asgore without fulfilling the requirements for the True Pacifist ending. The True Pacifist ending involves befriending Undyne and Alphys, exploring the True Lab, and facing Asriel Dreemurr.

14. Can I use a guide during my Pacifist run?

Yes! This is a common and perfectly acceptable practice. The game is complex, and using a guide can help you avoid mistakes and ensure you stay on track.

15. What happens after I complete the True Pacifist ending?

After completing the True Pacifist ending, you can choose to “reset” the game while keeping the memory of what happened, or choose to stay with your new friends. If you reset, some dialogue will be slightly altered to reflect your previous experiences. However, you must reset the game to obtain other endings, such as a No Mercy run.

How to do a perfect pacifist run in Undertale?