Yup, Leopold II was just insanely evil. He had illiterate tribal chiefs unknowingly sign their land away, and to avoid slavery accusations, the Leopold-led "Congo Free State's" people only labored unwillingly to "pay their taxes". To prevent the mostly indigenous patrols from revolting, their ammo was only replenished if they returned the right hand of a victim per bullet. They were underfed and needed to hunt, obtaining extra bullets by maiming innocent people. However, Leopold II was very good at managing PR, basically a trailblazer for modern politicians and CEOs, so few people understood the conditions the rubber was harvested under and he avoided consequences for policies that killed millions. Just as Congo gained independence, Belgium started a civil war to try to wrestle power back. The CIA also destabilized the region by various operations including the assassination of Patrice Lumumba.

A very good 3-part episode from Behind the Bastards podcast series on Congo: 1 2 3