In Roald Dahl's "Lamb to the Slaughter," do you think the wife feels any regret after killing her husband?
To answer this question, take a look at Mary's behavior after she commits the murder. As soon as she kills her husband, for instance, Mary is described as having a "clear" mind. In addition, she begins to quickly think about the potential punishment for such a crime. This fixation on herself and her fate implies that Mary is not at all remorseful about what she has just done, but is, in fact, only concerned about her own future and how she might evade arrest.
In addition, Mary does not dwell on the death of her husband but gets on with making herself look innocent. She goes to buy groceries, for example, and pretends to find her husband dead when she returns home.
Mary does, however, feel sad that her husband is dead. When she returns home from the grocery store, for instance, she "cries hard" and there is "no acting necessary."
Mary, therefore, feels sad about losing her husband but lacks any regret over her actions.
At the end of Roald Dahl's "Lamb to the Slaughter," there seems to be no regret from Mary for killing her husband with a frozen leg of lamb and then cooking for and feeding his police coworkers.
The narrator is very matter-of-fact when describing the task of Mary killing her husband, who had just come home and confessed that he wanted a divorce and was involved with someone else (this is implied, but not stated). The wife then goes downstairs, pulls out a frozen leg of lamb and wallops her husband in the back of the head. He collapses and dies immediately.
The narrator makes it a point to make sure the reader understands, "how clear [Mary's] mind became all of a sudden." This sort of eliminates the argument that Mary completed this act out of shock. While the murder can't be classified as premeditated, Mary's actions after the slaughter make it clear that not much remorse is involved.