Friedrich Nietzsche, a radical German philosopher, redefined modern thought with concepts like the "Übermensch" and "will to power." His critiques of religion and morality in Beyond Good and Evil and The Genealogy of Morals influenced existentialism and postmodernism. Despite debilitating health, his provocative ideas on human potential and nihilism remain foundational. Nietzsche’s legacy endures as one of history’s most daring thinkers.