Definition of penitent:

feeling or expressing remorse for misdeeds

Synonyms of penitent:

repentant, sorry, regretful, remorseful, contrite, apologetic, rueful, ashamed, penitential, sorrowful

Opposite/Antonyms of penitent:

shameless, unapologetic, happy, unrepentant, remorseless, impenitent, unashamed, unremorseful

Sentence/Example of penitent:

The penitent then leaves the confessional and goes and prays his penance in the church.