C.1900 Belgian crimes receive much greater international attention and condemnation, eventually they are pressured to release it to international "protection". It de facto becomes split, the south and east administered by the british to build their cape to cairo railway, the north and west administered as part of French West Africa, the lower Congo and the coast are jointly administered by the French, British, Portuguese, and perhaps also the Spanish, Germans, maybe still some belgian control. International observers are ensured to periodically travel the colony and ensure hands remain attached to their owners.
The new "protectors," especially the French and British, compete a bit to show how vastly superior, morally and technically, their empires are to each other and to the belgians.
Rubber continues to be exploited, but the workers are treated better and native Congolese are 'allowed' to reach higher ranks in companies.
Railways, roads, bridges, and canals are built, bringing the population a bit closer to the rest of the world, although much of the jungle remains very isolated.
Hospitals, schools, and even a few universities are built.
Dams and other powerplants, and factories are constructed, the Congo becomes an exporter of electricity of much of the continent.
World wars weaken the European powers, as well as force them to rely even more on native manpower for their armies, companies, and bureaucracies in the Congo. As nation-states emerge from the Austro-Hungarian and Ottoman Empires the colonies begin to be more insistent on their own independence. As one of the largest african states, and one with already unusual relation to the Europeans, and important resources, it is able to negotiate almost fairly. Independence happens early but gradually, effectively, and virtually absent of violence.
TTLs Congo has significant connections to the French, British, and Portuguese parts of Africa, and being independant very early attains very valuable trade and diplomatic relations with them. Its a large, wealthy, and centrally located state not just comparatively in africa, but worldwide. Kinshasa becomes the hub of rail, river, and air transportation in Africa, as well as the centre for finance and trade.
The massive population explosion in the midcentury fuelled by better education, nutrition, and healthcare, followed by a generation having less children and the opening international economy, made the Congo the economic 'Lion' along such Tigers as Korea.
By 2016 the Congo has an area over 2.3 million square kms, the 10th greatest in the world and comfortably the largest in Africa. Its population of over 130 million is also the 10th in the world, and only less than Nigeria in its continent. Its colossal natural resources of all types, vast manufacturing capabilities, and more recent expansion into the high tech industries powered by its eponymous river, has granted its people the 4th largest economy on the planet, at nearly 4 trillion USD of value produced in 2015. Per capita the Congolese enjoy a comfortable 30000 USD GDP/capita.