What ending did I get then? I killed all bosses but sans, ended with level 13, and sans called me at the end and told me to go t

neutral. you need to kill all the monsters and get to level 19

Oh. How do I do that? I killed everyone I ran into

when you use your save, it tells how many monsters are in the area

BRO

Yea u did it wrong
Reset

K

So in each area like snowdin or the ruins or hotland you need to find where monsters attack and run around n circles killing all of the ones you see until in your next encounter "but nobody came"

Yes

Kill them all.