18. Ronnie O’Sullivan
O’Sullivan is one of the greatest snooker players ever if not the very best. The six-time world champion is also the only player in history to have achieved over 1,000 century-breaks. O’Sullivan is truly a phenomenal talent and we may never see the like of him play again when he retires.
However, O’Sullivan has an extremely tumultuous relationship with his craft. The British player suffers from clinical depression and on multiple occasions has signaled his intention to walk away from the sport. He cites the high pressure as the main basis for this.