John Haigh
The Acid-Bath Killer
    

Began as a little swindler in England during WW2. He enjoyed inviting his victims to his so-called laboratory where he killed them and drank their blood. Then, he dropped them in a tank full of acid. He often robbed their money and/or values. He was hanged in 1949.
 

     
Victims: Olive Durand-Deacon, The Hendersons, The McSwanns, and The Search