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IMO the biggest problem of the Atlantic slave trade was there wasn't a lot of export commodities in the region. The slave trade I think can be curtailed significantly if the people in coastal West Africa had more profitable products for export. Here's a list of economic options I could see.
1. Ginger. This was the second most important noble spice after pepper and today Nigeria is one of the world's biggest producers. Somehow it would have to be introduced from Asia.
2. Sugarcane. Again another Asian/Middle East crop. If West Africa had the political organization to run sugarcane plantations locally, it might prove strong competition to Caribbean sugar.
3. Coffee. Mostly consumed by the Islamic world historically but by 18th century it would be in demand by Europeans.
4. Kerosene. Admittedly a bit out of the box. This is the only product that doesn't require the introduction of a foreign crop. There's plenty of petroleum in the region and the technique of distilling kerosene had been invented as early as the 9th century by al-Razi. IOTL kerosene lamp oil didn't become popularized until the 19th century as replacement for whale oil. Kerosene has another use as an insecticide against mosquito larvae when sprayed on ponds.