Mikhail Tal
The extent of Tal's alcoholism was quite astonishing. Vlastimil Hort, the top Czech player of the 1960s and 70s, has given a vivid account. Hort played at the Moscow tournament of 1963, with many of the top Russians. When he was due to play Tal, his opponent showed up very late, and drunk. He almost fell asleep at the board. Tal staggered away from the board, and returned with shaking hands, and unable to light a cigarette. Hort later found out that Tal had been grabbed by other Russians, and doused with cold water! Tal still managed to draw the game.