Dissociative villains are characters who have been diagnosed with or display signs of dissociative identity disorder (or multiple personality disorder) - these individuals have fractured psyches that make it appear as if they have more than one personality; one or more of these personalities are seen as obvious Sadists or otherwise dangerous (at least in fiction). In fiction, dissociative identities can occur from different circumstances: Mental Illnesses, Mutations, and/or Tragedies.

Do not add those controlled by Demons, Cosmic Entities, Deities, Aliens and/or other beings (for those, use Possessed/Brainwashed, Scapegoats and/or Pawns) unless their time spent being possessed ends up driving them mad - also, do not confuse them with Alter-Egos as they are simply alternate personas made to disguise the villains and perfectly sane individuals may have Alter-Egos for a variety of reasons such as keeping their identities secret much like how traditional heroes have disguises: Dissociatives literally see themselves as two or more individuals and are not in control of any changes. They can even be similar to but still not the same as Fragmental villains given that the evil part of the individual's mind as a whole is just a splintered fraction of who the character really is. However, if a dissociative is forcibly split from at least one of their other selves, they may overlap with fragmentals and can overlap with Alter-Egos if a personality is an entirely separate individual within the same person.

Be aware that dissociation has many different stages (just like psychoses), but dissociative identity disorder is simply the most extreme example. There are numerous other dissociative subtypes ranging from memory loss, post-traumatic stress disorder, or detachment from reality. They all share a common theme in the mind creating alternate personas and/or realities to try and shield itself from trauma. In the case of PTSD, a sufferer will instead be haunted with varying degrees of flashbacks that can be enough to cause villainous breakdowns during which they act out these events as if they were still occurring.

Dissociative identity disorder is one of the most controversial psychological conditions due to numerous false claims of this by sufferers of similar conditions such as schizophrenia, misdiagnosis by professionals, and even attempts by Psychopaths/Sociopaths to avoid punishment for severe crimes.

Prior to dissociation being recognized in psychology as an active condition spectrum that symptoms are associated with, it was blamed on demonic possessions or supernatural evils such as wicked creatures, many of which are still very prominent in the cultures and mythologies of the world.

Do not add the psychotic, mentally ill and/or psychopath/Sociopath categories to dissociative villains because this category is a subtype of mentally ill, and it would be redundant as all four of these categories are different in their own ways.

These types of villains generally don't count as Complete Monster given they have no control over their actions due to their illnesses. However, they can qualify if the Alter-Egos of the characters meets all the criteria and every heinous crime(s) are traced back to said Alter-Egos. The split personalities and original personalities are all heinous and show no regret towards their crimes, even being capable of knowing what their split personality did.