Ungar dominated the poker scene in Las Vegas by the force and brilliance of his betting and an intuitive talent for reading his opponents. He won the World Championship, held at Binion's Horseshoe casino, at the age of 26, in 1980, and repeated the feat the following year. After an extended period of ups and downs in his gambling, he returned to win the world title a third time in 1987.
For many years, Ungar had been the victim of his success, in becoming addicted to cocaine. The drug wrecked his health, in the process destroying his nostrils so badly that he took to wearing large round blue-tinted "granny" specs in order to hide his ravaged nose in photographs.
The game of the World Championship is Texas Hold 'em, a faster form of seven-card stud, which requires judgement, courage and card skills in about equal measure. Ungar had all the talents and had been widely predicted to repeat his back-to-back triumph in the championship in May of this year.
But he was suffering so acutely from his physical collapse that he was unable to leave his hotel room, despite the continued efforts of his close supporters to get him on his feet right up to the start of the event. During this time he also suffered delusions that people were out to get him, although, according to the Las Vegas police homicide unit, there was no indication of foul play in his death.
Nicknamed "the Kid" because of his youthful success, Ungar had an ability to dominate the table belied by his elfin stature. He was relentlessly aggressive and competitive. "Away from the table I'm really not that bad a guy," he said. "But when the cards are dealt, I just want to destroy people."
The irony was he destroyed himself in the process. In Las Vegas, the world champion has a celebrity status, which attracts not just the admiration of poker players, but of other gamblers, women, fans and money.
Despite the huge sums won and lost in the top level games - the world championship prize is $1m in cash - a player can rapidly go broke. When that happens, new backers are always eager to take a share of his action. The result is that for most of the time such a player is not really playing for himself, and money loses all meaning.
Ungar first came to attention at a young age in New York, where he had the reputation of being the strongest gin rummy player in the city. He grew up in Manhattan's Lower East Side where his father owned a bar. Ungar had a gift for mathematics and, as he put it, a sixth sense about cards.
His father died when the boy was 13 and a year later his mother suffered a stroke. Ungar had to support himself and his family by hustling at cards. His skill at gambling was honed by playing with the wise guys who hung out at his father's tavern. The only trouble was, he was so successful at gin he wiped out his opponents, and with them his source of income. When he moved west, the same pattern was repeated in Las Vegas.
Seeking opportunity elsewhere, he turned to high stakes poker, and rapidly established himself. He won the World Championship at his first attempt, thus becoming the youngest title holder up to that time, and showed that his success was no fluke by winning several other big tournaments. No-limit Hold 'em was seen as his best game.
Stu Ungar, poker player: born New York 1953; one daughter; died Las Vegas 22 November 1998.