Former world chess champion Bobby Fischer died on Thursday. Fischer was the only non-Soviet player to become world champion between 1948 and the fall of communism. Many experts consider him the greatest chessmaster of all time. During his last three years of competitive play (1970-72), Fischer not only defeated his opponents but totally dominated all the other top players in the world to a still-unsurpassed extent. His achievement is all the more remarkable in light of the fact that he mostly worked alone and was up against a massive chess "machine" lavishly subsidized by the Soviet government. Dmitry Plisetsky and Sergei Voronkov's fascinating book, The Russians vs. Fischer (based on internal Soviet documents released after the fall of the USSR), has numerous details about the Soviet effort to prevent Fischer from winning the world championship. It also documents the enormous respect that Fischer won from his Soviet chess rivals.
Unfortunately, as the AP obituary linked above notes, Fischer rapidly descended into delusional paranoia and anti-Semitism after winning the world championship in 1972. He refused to defend his title in 1975 and spent most of the rest of his life in seclusion, becoming increasingly more deluded as time went on. While no opponent could consistently beat him at the chessboard, the demons in his own mind ultimately defeated him far more completely than any rival grandmaster ever could have.
UPDATE: Garry Kasparov comments on Fischer's death here.