Socrates A. tutored Alexander the Great B. condemned to death by poison C. thought philosopher-kings should run the government

B. Condemned to death by poison

In Plato's Apology, we learn that Socrates has been angering important people in classic Greece (he goes around questioning statesmen's knowledge, and determines that most of them overestimate their knowledge). Eventually, Socrates is sentenced to death by ingesting poisonous hemlock.

Bonus: If you're ever in NYC, visit the Metropolitan Museum of Art and check out Jacques-Louis David's painting depicting Socrates' death.