Portugal hands down. They were the first to colonize Africa, created the West African slave trading economy, single-handedly disrupted the Arab trade routes in East Africa and thus decimating that regions economy, instigated tribal conflicts that led to centuries of civil war which they profited from, and exported more Africans during the African holocaust than any other nation. Most other European powers didn't get their foot in the door raping Africa of it's people and resources til about 120 years ago but Portugal has been doing it since the 1500s