Virus!Dust. Lore: Sans gets infected by a virus that makes him act weirdly and unpredictable. His presences corrupts the world around him. His attacks take away makes HP. His victims always end up a lifeless broken glitched sprite. It is unknown if he actually gains LV or the virus itself heightens his stats. Often faces memory lost. This sans was already a dust sans, the virus happens after a dust timeline restarts. The copy of UNDERTALE the player used was pirated hence leading to the virus.
Song- The virus by Dorkel_dob