regret A2

/ɹɪˈɡɹɛt/ To feel sorry about something you did or did not do.

regretful C2+

/rɪˈɡrɛtfl/ feeling or showing sorrow or remorse

regretfully C2+

/rɪˈɡrɛtfəli/ with regret or a feeling of sorrow

regrettable C2+

/rɪˈɡrɛtəbəl/ giving cause for regret; unfortunate