re ‧ gret ‧ ful /rɪˈɡretf ə l/ BrE AmE adjective
[ Word Family: adverb : ↑ regrettably , ↑ regretfully ; adjective : ↑ regrettable , ↑ regretful ; verb : ↑ regret ; noun : ↑ regret ]
someone who is regretful feels sorry or disappointed:
She apologized and sounded genuinely regretful.