Atlantic Slave Trade
https://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Official_medallion_of_the_British_Anti-Slavery_Society_%281795%29.jpg/170px-Official_medallion_of_the_British_Anti-Slavery_Society_%281795%29.jpg (jan 1, 1502 – jan 1, 1804)
This was an event that nearly lasted 300 centuries because of the various European countries that participated in it. The Europeans exploited the Africans because they were easy to get from the coast and millions of Native Americans perished from the diseases of the New World. Slavery was very bad for the economy because when so many people are being exploited for their work and not getting paid (in money) that will cause crashes in the economy. In addition, it also creates job losses because the Africans are doing free-labor that could have resulted in a European person getting that for their livelihood.
Added to timeline:
Economy of the late 17th to the 18th century Europe