Corky at #11 refers to the "Dark Triad Personality." It's a doozy.
All three dark triad traits are conceptually distinct although empirical evidence shows them to be overlapping. They are associated with a callous"manipulative interpersonal style.
Narcissism is characterized by grandiosity, pride, egotism, and a lack of empathy.
Machiavellianism is characterized by manipulativeness, indifference to morality, lack of empathy, and a calculated focus on self-interest.
Psychopathy is characterized by continuous antisocial behavior, impulsivity, selfishness, callous and unemotional traits (CU), and remorselessness.
en.wikipedia.org
They are ... until it's no longer advantageous.