Undertale Routes: Pacifist AKA True Pacifist Route

  Hey there! This is the last of the three main endings to Undertale although there are a few more endings that I'll cover. Also, I'm sorry this wasn't put up when I said it would be, but sadly life made it's appearance. Anyways, make sure to check out the other posts in this series if you haven't already and let's jump right in!
ALERT! SPOILERS AHEAD! IF YOU HAVE NOT YET COMPLETED THE GAME, YOU MAY WANT TO COMPLETE IT BEFORE READING THIS POST! TREAD CAREFULLY.

There are two ways to achieve a pacifist ending, and neither of them can happen without a full play through before it. This means that you cannot achieve the pacifist ending on your very first play through of the game. In this post, we are assuming that you have completed one of the neutral routes prior to completing the pacifist route. This leads to the pacifist route that we call the "True Pacifist Route". This is also considered by many to be the "true ending" to Undertale since there is a happy conclusion and complete credits.

   In order to reach the True Pacifist ending, you have to follow one simple rule: Don't kill. You cannot achieve this route if you gain any EXP or LV. It won't count if you FIGHT or destroy the Dummy in the Ruins since these do not give you any EXP. If you do kill a monster, you can reload your SAVE file and all will be as if it never happened. There are a series of actions that you have to follow in order to keep your run from being turned into neutral. Here they are in order.

1. After fighting Papyrus, go to his house and go on a date with him.
2. After Undyne passes out pursuing the protagonist, pour water on her face from the water cooler.
3. Go back to Waterfall and visit Undyne's house. Papyrus will be waiting outside and you should talk to him so you can enter the house. Complete the cooking lesson and fake battle with Undyne.
4. Go through Hotland and the CORE and get the ratings of Mettaton EX up to 10,000 (including using Alphys' phone upgrade to shoot at his heart during some of the rounds) to end the battle peacefully.
5. Backtrack from the CORE to the MTT Resort, where the bridge connects the two places. Undyne will call the protagonist and ask them to deliver a letter for her.
6. You have to talk to Undyne outside Papyrus' house to get the letter. If you haven't gone on a date with her when the protagonist reaches the bridge, you need to backtrack, and go on the date with her and then she'll give you the letter unless your inventory is full in which case you still have to go to Papyrus' house. If you discard the letter, you can return to Undyne and receive Undyne's Letter EX which cannot be discarded.
7. Put the letter under the door of Alphys' lab and complete the date with her.
8. When you leave the Garbage Dump, Papyrus will call you and tell you to meet Alphys at your lab. Go back to the lab and you will find a note leading to her "bathroom" which contains the True Lab. Once you enter the True Lab, you cannot abort the True Pacifist Route.
9. Find the four keys in the True Lab and put them in the correct slots to open the generator room. Turn on the generator to trigger a conversation with Alphys. Head back to the elevator near the generator room to be warped to New Home with the exit vined off. This tells you that the True Pacifist will occur. This also subsequently means that you can't leave New Home but you won't need any items in later battles.

Something cool about this route is that it is the only one in which you learn that the protagonist's name is Frisk. If you try to name the fallen human Frisk at the beginning of the game, it activated Hard Mode. If you've played through the True Pacifist Route before, then you'll find a picture of the protagonist standing with Sans and their friends in his lab. This is presumed to be the picture shown at the end of the game if the protagonist chooses not to stay with Toriel.

There are some more fun facts and small tidbits that I'll let you figure out if you haven't already! Hope you have fun playing and reading! Bye!