Synonyms of regretful

2 Syllables
mournful, guilty, rueful, guiltier, guiltiest
3 Syllables
guilt-ridden, contrite, compunctious, penitent, sorrowful, godawful, nostalgic, ashamed, repentant
4 Syllables
disappointed, accusable, convictable, attritional, self-reproachful, penitential, lamentable, remorseful, shamefaced
5 Syllables
apologetic