Whether you think they are evil, disturbed, or just mental you are part of a society that exhibits both a repulsion and fascination with the lives and minds of serial killers. Who are these serial killers and what motivates them? We really don’t know. But when we can skillfully create torture devices meant to inflict the most pain on another individual, we are afraid to know the answer. These are the 25 of the most evil serial killers of the 20th Century.