Final answer:
Frederick Douglass stands out as the most famous immediate abolitionist, known for his powerful oratory, influential writings, and lifelong dedication to ending slavery and achieving freedom for all enslaved people.
Step-by-step explanation:
The most famous immediate abolitionist was undoubtedly Frederick Douglass. Born into slavery, Douglass became a prominent figure in the abolitionist movement after his escape to freedom. A skilled orator and prolific writer, he dedicated his life to the cause of liberating all enslaved people and was a key member of the Anti-Slavery Society. His autobiographies, including Narrative of the Life of Frederick Douglass, an American Slave, were crucial in advocating for the humanity of black Americans and the immediate end to slavery. Douglass's influence was so significant that his efforts helped shape the radical abolitionist movement that aimed for swift and complete emancipation.