From Longman Dictionary of Contemporary Englishregretfulre‧gret‧ful /rɪˈɡretfəl/ adjective SORRYsomeone who is regretful feels sorry or disappointed She apologized and sounded genuinely regretful.
Examples from the Corpus
regretful• There wasn't much else to see, Malcolm Anderson told Jean, sounding regretful.• He did not crave recognition, but was understandably regretful about his lack of it.• She cast a regretful look at the big double bed with its luxurious continental quilt.• With a regretful sigh he removed his arm from its protective place around her shoulders and stepped back.• Whispered in reverent and regretful tones, the rumors had been floating for the past few weeks that her condition had worsened. 