Undertale - Nintendo Switch

Undertale has 3 different routes, each with their own story and boss fights: Neutral, Pacifist, and Genocide. However, the latter two routes require specific actions from the player throughout the game.

In Pacifist, you must not kill any enemies. If you find yourself in a battle, you either run away or use the ACT command to try and spare the enemy (only the Dummy at the beginning and Mad Mew Mew can be killed without breaking this rule). After confronting Undyne, she will faint from the heat in the Hotlands. Here, it’s essential to take a cup of water from the water cooler and give it to her; otherwise, you'll lose your chance to complete the Pacifist route. Pacifist also requires that you have completed the Neutral route at least once, but you don’t need to play through the entire game twice. You can simply start by playing the game without killing any enemies and save right before the final boss. This will still be the final boss of the Neutral route. Defeat them and go through the entire credits. Now, load your save just before the final boss; you can now complete the remaining requirements for the Pacifist ending:

1. Go to Papyrus's house in Snowdin and go on a date with him.

2. After that, head to Undyne's house in Waterfall and have a date with her too.

3. Now, you need to go to the entrance of the Core, where Undyne will call you asking to deliver a letter for her.

4. Undyne will be waiting for you at Papyrus's house to hand you the letter.

5. Go to Alphys's lab in the Hotlands and slide the letter under the door; you will also have a date with her now.

6. The date ends in a junkyard, and Papyrus will call you to say you need to visit Alphys again in her lab. Once there, you’ll find a note that leads you to her bathroom, but it actually takes you in a lift to the True Lab. From this point on, you are forced into the Pacifist route and cannot exit.

7. Complete the puzzles in the True Lab, and you will be taken to the final location of the game. You are now ready to fight the Pacifist final boss.

Genocide, on the other hand, is the complete opposite. You must wipe out everyone. In every location (starting from the Ruins all the way to the Hotlands and the Core), you need to keep triggering wild encounters and kill the enemies. You must do this until you enter another wild battle but receive the message "But nobody came." This means you are done in that location and can move on to the next one. From Snowdin onwards, save points will tell you how many enemies you still need to kill in the current location.

I’ll discuss Neutral last because you first need to know what the other two routes entail. Neutral is literally what lies in between; you don’t spare everyone, but you also don’t kill everything or everyone. Of course, as I mentioned, this route must be completed before you can achieve the Pacifist ending. So, if this hasn’t been done yet, the Neutral ending can still be obtained if you spare everyone. If it has been completed and you spare everyone but don’t carry out all the steps mentioned above, you will still receive the Neutral ending.