Undertale is the primary universe that gave birth to the many alternative universes that exist now.
The Neutral Route was Frisk's first route in which she chose to kill some, but spare the other monsters for the sake of having a chance against Asgore. Since she'd chosen to kill minor monsters (Froggits, Whimsuns, Vegetoids, etc) and no major characters, there appeared to be no significant impact until she murdered Asgore. After the death of the king and Frisk returning to the surface, chaos ensued within the Underground due to it’s lack of a leader. Upon learning about the countless problems in the Underground, Frisk RESETS.
True Pacifist Route