A madman who takes his time to turn on his chainsaw before relentlessly chasing the player around, vigorously slashing everywhere in front of him. He is first found in the Mystery Manor, and later reappears in the kitchens under the Library inside of Dracula's Castle, an area more suitable for an enemy of these characteristics.
The Mad Snatcher, an enemy encountered later in the game, uses a modified sprite of this enemy, although featuring no significant additions to its behavior other than dealing more damage.
The Mad Butcher is most likely based on Leatherface, the main antagonist from the horror film series, The Texas Chainsaw Massacre. Both characters look virtually the same, right down to their bloody apron, fuzzy black hair, and mask made of human hide.
This enemy is rather inaccurate from a narrative point, considering the modern chainsaw was not invented until the twentieth century.