When you feel compunction you feel very, very sorry, usually for something you did to hurt someone or mess something up. When you feel no compunction, you're not at all sorry.
The noun compunction comes from the Latin verb compungere, meaning “prick sharply.” When you feel compunction, you feel a sharp prick of your conscience. The word compunction is often used in the negative in phrases like “without compunction” or "no compunction." You might say that the burglar acted without compunction when he stole your baseball card collection.
n a feeling of deep regret (usually for some misdeed)
guilt, guilt feelings, guilt trip, guilty conscience
remorse caused by feeling responsible for some offense
penance, penitence, repentance
remorse for your past conduct
a deep feeling of guilt often experienced by those who have survived some catastrophe that took the lives of many others; derives in part from a feeling that they did not do enough to save the others who perished and in part from feelings of being unworthy relative to those who died