Undertale sans the hardest boss

Ink！Sans Fight by 我素系统！ - Game Jolt

Bad Time Simulator - Sans Fight

Sans Simulator 2 Player Edition

undertale two player sans fight - Physics Game by ninjamineturtle

Player!Sans (Sans The Player), Balanceverse Wiki

Sans/Dusttale, New Undertale Fanon AU Wiki

Sans vs Chara 2 player on Scratch

Sans Undertale Wants to Play by WaffleGolem on DeviantArt

Jevil 2 Player Fight V1.18 - TurboWarp

A cool little detail about Sans this guy brought up in the Stronger Than You animation by alfa995 : r/Undertale