Once Chara has recovered they continue through the Underground until they reach the border between the two forces. As they travel they discover a strange power that they possess, the Resets. At this point there are a couple of different routes they can choose;

Pacifist- They befriend the monsters of The Reprisal, proving that not all humans are bad. Though not freed the monsters, along with Chara, live together peacefully.

Neutral- They focus on escape, killing some monsters and leaving the Underground. Those that remain are devastated, their hope wildling away, end the fight for it no longer seems to have a purpose.

Genocide: Peace For All- They kill all those in The Reprisal. The monsters, thankful that the war has ended, ask for Chara to stay. Whether they agree or not, the remaining monsters prepare for the next human to fall.

Genocide: No Forgiveness- They join The Reprisal, seeking the elimination of all other humans. Chara returns to The Redemption, killing all that refuse to join. Once the job is done they are sent to the surface, given the task to release the monster and help take out humanity.

Genocide: Escape is Futile- They start off killing The Reprisal before heading back to take out the rest of monster kind. When the task is completed Chara prepares for wat comes next. The elimination of humanity. The power of the resets goes to their head.