Frisk

Frisk is the main protagonist of Undertale.

Appearance
Frisk has yellow skin, closed eyes, and brown-red hair. The protagonist wears a light blue and magenta striped shirt, brown-red pants, and brown-red shoes.

Pacifist
Frisk shows MERCY to the monsters in the Fields, remaining on a pacifist route. Sans invites the human to go to Grillby's. Afterwards, Alphys asks Frisk to test her time machine. Frisk does so, and after that, Alphys asks them to take a photo of her and Undyne about to kiss. Instead, the protagonist accidentally changed the timeline. Frisk then goes back to the past to warn Alphys not to let anyone use the time machine. Because of this, the protagonist disappears.

Neutral
Same as pacifist except Frisk kills a few monsters, and Sans takes notice.

Genocide
Frisk exhausts the kill count, immediately entering Uppertale's "No Return Point" in the Genocide run. After this, Frisk kills Sans, Papyrus, and Flowey. After killing all that can be killed in Uppertale, Chara appears and destroys the world.