IMO, korchnoi is the greatest player never to become WC. he won the USSR championship 4 times (1960, 1962, 1964 and 1970), and was 2nd or =2nd twice (1954, 1961). his 45-year tenure near the top of world chess (<1960 to the present) is astonishing, and he continues to play top-rank chess even today, in his late 70s.

he had a large plus score against tal (+13 =29 -6 in chessgames.com). this is a collection of some of his refutations of tal's attacks.