Final answer:
The Duke's complaint about his late wife in Robert Browning's poem 'My Last Duchess' was that she was too easily pleased and showed appreciation for simple things.
Step-by-step explanation:
In the poem "My Last Duchess," the Duke expresses dissatisfaction with his late wife's behavior. He reveals that she was appreciative of everything around her, from nature to art. The Duke, however, sees this as a flaw, implying that she should have reserved her admiration exclusively for him. The complaint suggests the Duke's possessiveness and desire for complete control over his wife's emotions and preferences. His jealousy and need for dominance are evident as he describes her smile as equal to any other object of desire.
Furthermore, the Duke mentions the term "stooping" to signify his disapproval of his late wife's humility and lack of pride. He implies that she lowered herself by treating everyone with kindness and appreciation, suggesting that he expected her to be more exclusive in expressing such sentiments. The Duke's complaint unveils his authoritarian nature and the twisted sense of power dynamics in his marriage. This revelation sets the tone for the poem, providing insight into the Duke's character and contributing to the overall theme of control and possession.