Then you have Maureen Connoly, whose story makes Seles seem lucky. She won nine GS titles before turning 20, winning every final and losing only one set (in the first of those, when she was 16). A fall from a horse, caused by a truck, put a stop to her career before her 20th birthday. Add to this that she died of cancer at age 34, and you have if not the greatest certainly the most unlucky player of all time. Finally, Suzanne Lenglen. She managed to win 8 GS titles, which may not seem impressive.
Macho man the cream of the crop shirtBut in a career hampered by the prohibitive travel conditions of the time, the first world war, various health problems she lost only seven matches. Not in a year, in her whole career.Obviously that would be impossible today, hence my remark about comparing players of different epochs. But certainly only Lenglen in the twenties and Connoly in the fifties have been so dominating. Lenglen died of leukemia at 39. I give thus nine candidates to the title you ask about. To reach ten, I would add Molla Bjursted-Mallory, another singular story, since she started competing when she already was in her thirties and went on to win her eight US open at the age of 42. Here we can ask the reverse question: how many titles would she have won had she started playing earlier?