Toussaint understood how to use yellow fever to his advantage. The invaders didn't have enough respect for the disease.
Toussaint also recognized that while his enemies numbers would dwindle, they (the Spanish, French, and British) would bribe and coerce his own men and play politics against him. So he mostly avoided direct battles or even small engagements, and focused on keeping his own house in order. It worked for years. The losses the Europeans piled up were nightmarish. Eventually, towards the end of his career, he was betrayed and captured. But the Europeans had ravaged Haiti by then, and all removing Toussaint did was destabilize the country further, in fact leading to the massacre of every white person who lived on the Island. They didn't realize Toussaint was actually holding back for the whole war, refusing to give in to racial hatred. Toussaint had close white friends who fought with him, he thought racism, anti-white or anti-black, was an abomination. His younger lieutenants didn't always agree. Once he was out of the picture, his men went wild.
Great podcast on the subject:
https://recordedhistory.net/the-age-of-napoleon/
and for a more scholarly look, google Tom Devine. He's the leading scholar on Henry Dundas's life.