Dear  Marcelo Negri Soares,

 A general characteristic among psychopaths

is lack of empathy but you cannot recognize  them, because they are all over among us (5%) in every profession an in every position. (Also here on RG you can read comments such as women are easier to deceive!).  It takes many years of studies and tests to understand this. Robert Hare has done extensively research on this topic and Sam Vaknin's book "The malignant self" sheds ligth on the issue. The psychopaths seem to be normal or too good to be true (and then they are not true)

Common Characteristics Among Psychopaths

The following characteristics of a psychopath are defined by Hervery M. Cleckley in 1941 in the book  Mask of Sanity:

Superficial charm and average intelligence.

Absence of delusions and other signs of irrational thinking.

Absence of nervousness or neurotic manifestations.

Unreliability.

Untruthfulness and insincerity.

Lack of remorse or shame.

Antisocial behavior without apparent compunction.

Poor judgement and failure to learn from experience.

Pathological egocentricity and incapacity to love.

General poverty in major affective reactions.

Specific loss of insight.

Unresponsiveness in general interpersonal relations.

Fantastic and uninviting behavior with drink, and sometimes without.

Suicide threats rarely carried out.

Sex life impersonal, trivial, and poorly integrated.

Failure to follow any life plan.

This is not necessarily true for every psychopath.