Which social problems did Mark Twain criticize in his late essays?

In his later years, Mark Twain utilized polemical essays to express his moral indignation regarding several significant social and political issues. His critiques during this period focused on:

• Antisemitism: Addressed in his essay "Concerning the Jews" (1899).1
• Imperialism: Denounced in his work "To the Man Sitting in Darkness" (1901).1
• Lynching: Criticized in the essay "The United States of Lyncherdom," which was published posthumously in 1923.1
• Colonial Exploitation: Targeted the brutal rule of Leopold II in the Congo in the pamphlet King Leopold’s Soliloquy (1905).1

While these late essays were noted for their earnestness and lack of the palliative humor found in his earlier works, they were consistent with Twain’s lifelong opposition to greed, cruelty, violence, and corruption.1