UnderFell Sans Fight I (Fan Game) - Free Addicting Game

Player has passed another path of genocide. Sans was tired of watching all this. And after the Ruins, Sans immediately attacks a person. You have a small LV. You have to win. (The game is in DEMO)

For you, what was the best boss fight in Undertale? - Quora

Underfell (ManiaKnight), Undertale AUs Wiki

Tanphrous, Godverse Wiki

Underfell Sans Genocide Fight [Mockup] by Tendo63 on DeviantArt

Tanphrous, Godverse Wiki

Game Jolt - Share your creations

Undertale Sans Pacifist Fanmade Battle

Are there any other games featuring a combat system like the one in Undertale with all the dodging? - Quora

UnderFell Sans battle for Android

Undertale: Underfell by Team-UF - Game Jolt

Underfell Sans fight by MelonCrab - Game Jolt

UnderFell Sans Fight I (Fan Game) - Free Addicting Game

Undertale / Memes - TV Tropes