Mikhail Tal
In 1960, at the age of 23, Tal defeated Mikhail Botvinnik in the Moscow World Championship match, by 12.5–8.5 (six wins, two losses, and thirteen draws). This made him the youngest-ever world champion, a record later broken by Garry Kasparov. Botvinnik, who had never faced Tal before, won the return match against Tal in 1961 by 13–8 (ten wins to five, with six draws). Between the matches Botvinnik thoroughly analyzed Tal's style, and turned most of the return match's games into close manoeuvres and endgames, rather than the complicated tactical melées which were Tal's preference.