Ai means sorrow, regret, and sympathy. "Sorrow for someone's misfortune" means feeling sad for someone's misfortune. Nu means anger and regret.

"Being angry but not fighting" means feeling angry and regretful about someone or a certain downturn, not fighting against someone or a certain downturn. The meaning of the whole sentence is to feel sad for someone's misfortune, and feel angry and regretful that he/she did not fight and failed to live up to expectations.

From Lu Xun's "Moro Poetry Mechanics"

Lu Xun's phrase "sorrowful for his misfortune, angry for his inability to fight" is often understood as his attitude towards Kong Yiji. Actually not, or not entirely.

This is what Lu Xun used when commenting on the British poet Byron in his essay "On the Power of Moro Poetry" before writing his novel in 1907. A few sentences in the original text say: "(The poet) values ??independence and loves freedom. If a slave stands in front of him, he will feel sad and look down on him. He will be sad because he mourns his misfortune, and he will be angry because he will not fight..." It was Lu Xun who spoke of Byron's attitude towards his unconscious British compatriots.