The unnamed Murderous Wife is a villainess from "For Pete's Sake," episode #44 of Goof Troop (airdate November 5, 1992). She is the plot-twist main villainess from the episode's program-within-a-program.
The episode has Pete believing that someone is out to kill him, and in the midpoint of the episode, Pete (under Peg's suggestion) sits in front of the TV and watches a program where a woman serves her husband warm milk to help him sleep. The husband suspects a peculiar taste, only to suddenly realize that he has been poisoned. Though his deduction is correct, it came too late, as he succumbs to the poison and dies.
Shortly afterwards, the wife turned heel and revealed that she poisoned her husband, and following her admission, the evil wife cemented her heel persona by cackling maniacally over her villainous actions. Pete turned off the TV, feeling more nervous than ever, leaving the fate of the maniacal villainess unknown.