For example, everyone knows the details of the Barbary, Arab, Ottoman, Caucasus, Saharan, and Andalusian slave trades, and countless movies were made showing how whites suffered under them, and their mythologized wars to end them. Some were even made showing Blacks' suffering under the Saharan slave trade, as it was politically useful for whites to demonize Arabs.
However, did you know Europe and its colonies also engaged in slavery? Before the US abolished slavery in 1865, 12 million Black slaves were shipped to the Americas. Mostly to South America, but some to North and the US as well. That may be less than the estimated 11-17 million the Saharan slave trade claimed, but it's hardly something we should ignore.
Of course the white people in charge aren't comfortable publishing this, so it has been relegated to the footnotes of history.