shameless

1. Feeling no shame; impervious to disgrace.

2. Marked by a lack of shame: a shameless lie.

Synonyms: These adjectives apply to that which defies social or moral proprieties and is marked by a bold lack of shame. Shameless implies a lack of modesty, sense of decency, or regard for others' rights or feelings: a shameless liar; a shameless accusation.
Brazen suggests flagrant, insolent audacity: a brazen impostor; brazen arrogance.
Barefaced specifies undisguised brazenness: a barefaced hypocrite; a barefaced lie.
Brash stresses impetuousness, lack of tact, and often crass indifference to consequences or to considerations of decency: a brash newcomer; brash demands.
Impudent suggests offensive boldness or effrontery: an impudent student; an impudent misrepresentation.
Unblushing implies an inappropriate lack of shame or embarrassment: an unblushing apologist; unblushing obsequiousness.