For a person with multiple personalities, can one personality murder or kill another personality such that the killed personality never surface again?
Did it ever happen or studied?
Far from being simply encoded in the genes, much of personality is a flexible and dynamic thing (Mischel & Shoda, 1995) that changes over the life span and is shaped by experience (Roberts, Walton, & Viechtbauer, 2006). Can Personality Be Changed? by Dweck
After searching for related case studies, this is the closest I could find: "Deathman, age 27, intervened when John, Gail and Diana argued." -- Four Cases of Supposed Multiple Personality Disorder: Evidence of Unjustified Diagnoses This women's multiple personalities fought each other (even though the authors doubt she had MPD).
Perhaps "kill" is not the best word.
In working with MPD patients, I understand the creation of personality in the context of MPD to be different than the creation of personality of the core individual. Our personalities are formed both from DNA and from our interactions with our environment. In the case of someone who has MPD, each personality serves a purpose. Occasionally, individuals with MPD will develop a personality that demonstrates dominance or the need to fight. This dominance or fight instinct is their primary coping mechanism. If this particular personality feels threatened by one of the other personalities, or perceives one of the other personalities to be weak (causing weakness of the whole), then the one can attack the other. How the brain creates or destroys personalities of an MPD is unknown. Most often it simply appears that the personality that was attacked is hidden, dead, or reabsorbed into the collective. The thoughts, feelings, and even memories from that personality can simply be gone. Where they "go" is also unknown. It is not believed that a formed personality is stored in memory the way we store other known information. It isn't like amnesia. But, there can be clear gaps in what one remembers. The core personality will often recall that there was once a personality that existed, but will be unable to recall the details held by that personality.