How to set correctly utf8 on oracle?
Based on your reply of 

SELECT ASCIISTR(titolo) FROM generale WHERE titolo LIKE 'Roma drogata%;

TITOLO                                                      
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Roma drogata: la polizia non pu\FFFD\FFFD intervenire


You get Roma drogata: la polizia non pu?? intervenire because it has been inserted wrong into your database, i.e. when the record was inserted the client had set NLS_LANG wrong.

Unicode character U+FFFD is this one: REPLACEMENT CHARACTER

Probably the SQL script was saved as UTF-8 but NLS_LANG was set to ISO-8859-1 or Windows-Cp1252 or similar.