Feeling ashamed for less than honorable actions is a normal human reaction.
If such emotion is absent, then it is worth thinking about the reasons.
Experts note that this type of people is extremely difficult to build relationships of any kind. Sociopaths make unreliable partners, bad friends, and not the best colleagues.
Sociopaths always think only about personal gain.
If they do something bad, it was good for them personally. Therefore, there can be no talk of a feeling of shame: they cannot experience this emotion.
This is a difficult case, because you need to convey to the person why exactly he was wrong. Not everyone is ready to accept such information.
Many people are convinced that they are always right. Therefore, they rarely feel ashamed.
This case is similar to the first point, but people have different motivations. Narcissists are sure that they are impeccable in everything, so they "could not" make the wrong decision.