Antonio Fabiani is portrayed as somewhat shady character in the series, he's an Italian businessman who frequently seeks to establish new commercial ventures with various investors. Unfortunately, some of these businesses fail, resulting in financial losses for his investors. Despite this, Antonio remains focused on acquiring wealth and is not above employing questionable methods to achieve his goals.
In the series, Antonio first encounters Nadja at a masked ball, but it's during their subsequent meeting in Italy that she truly comes to recognize his unscrupulous nature. Despite this, Nadja eventually learns about Antonio's upbringing in Venice and begins to understand that people are not inherently good or bad. She hopes that one day he will find a more ethical path in life.
Personally, I believe that Antonio's scheming ways ultimately prove beneficial later in the series.