Hi, OP. Lemme see if I can help.

Couple of prefatory notes...

I've noticed that sometimes, in this sub, an OP can get ignored or answered snarkily for asking "the wrong kind of question." I disagree with this approach because I feel like curiosity is good and if you can help someone, you ought to. Still, sometimes it's also a good idea to pick apart assumptions underlying a question, just to be clear about what it is we're talking about.

So firstly, "best" and "worst" are subjective evaluative terms, so any answer is going to be heavily qualified. Which is okay. What's a bit less okay can be this "oppression olympics" thing, in which people debate who had it worst as a way of determining whose complaints are valid. The thing is, in my personal opinion, there isn't a valid moral or ethical justification for European imperial practices in Africa (or anywhere). So anyone with a legit grievance has, in my opinion, an equal right to state it and to be heard and to be thought of as having a legit grievance. (Some scholars would tell me to STFU about my personal opinions, but I work within a school of scholarly inquiry related to Subaltern Studies, and we typically like to acknowledge our personal biases, in part as a way to help others determine whether what we're saying is more or less trustworthy.)

Secondly, your question is complicated by the fact that the lived experience of an "average" person (this is a squishy term, but I'll run with it) in a specific place is likely to have been qualitatively different at different periods under the same colonial power. In response to abolitionist and anti-colonial activists in metropolitan locations, some colonial powers improved what we might call their human rights policies as time went on. Also, and probably something that had more of an impact, or at least as much impact, as protests back in Europe, African people began to organize and agitate for their own rights as time went on, which also sometimes resulted in improved conditions for people.

Thirdly, an important resource for answering this kind of question is the colonial record--that is, the body of texts written by colonial administrators themselves. That record is, predictably, biased in favor of the Europeans and their actions. Of course there are many other texts that we can turn to for other perspectives, but sometimes, as in the case of a genocide, it can be difficult to determine exactly what happened since most of the people who could tell about it died without being able to tell what they experienced. (See Veracini's chapter in Empire, Colony, Genocide: Conquest, Occupation, and Subaltern Resistance in World History, ed. Dirk Moses, 2008.)

Finally, colonial powers like Britain and France practiced divide and rule tactics, such that an "average" person of one ethnic or ethno-linguistic group might have had a much better quality of life than someone of a less privileged group of indigenous African people. I think in any colonial space you find a sort of a comprador class, too--elites who cooperated with Europeans, or non-elites who improved their lot in life through cooperation and thus became part of the comprador elite. So you get into hot water if you totalize an "average" person's experience too much.

So...it's a big question. If I had to rephrase it to make it easier to answer, I'd phrase it this way: Which European colonial dispensations had the harshest, and also the least harsh, policies towards indigenous, non-comprador African people? And I think what you'll find is that the answer you get is not something like "the French were the least bad and the Belgians were the worst," but rather "Incident X was terrible. So was Incident Y. So was Policy Z." So you get specific examples. And the same would be true for an historian's response to the question of more "benevolent" colonial dispensations.

So here's my selective, subjective, and extremely limited answer to my interpretation of your question.

The Germans made a graveyard of their spot of southwest Africa. In the English translation of Genocide in German South-West Africa: The Colonial War of 1904–1908 and Its Aftermath (edited by Jürgen Zimmerer & Joachim Zeller, trans. by Edward Neather, Merlin Press, 2008), the Germans killed 80% of the Herero people and more than half of the Nama people. One of the only reasons that we know that this happened, and that we can be relatively certain of the actual figures involved, is that the Germans were super proud of what they had done, and publicized it. Also, when the British were looking for excuses to kick the Germans out of southwest Africa, they actually went and interviewed the (few) survivors of German genocides. So we actually do have records from indigenous African perspectives too, which is rare.

I would also cite Leopold II's Belgian Congo as a site of colonial genocide. From Tim Stanley's article "Belgium's Heart of Darkness" in History Today, Vol 62, Iss. 2 Iss. 10:

Leopold's hell operated by an insane logic. Villages were set quotas of rubber and the gendarmerie were sent in to collect it -- a process that was sped up by looting, arson and rape. If a village failed to reach its quota hostages would be taken and shot. To ensure that the gendarmerie didn't waste their bullets hunting for food, they were required to produce the severed hands of victims. As a consequence a trade in severed hands developed among the villagers and those police that couldn't reach their quotas.

Estimates of the number of people who died directly--through violent murder--or indirectly--through starvation or because of other conditions caused by Belgian policies--vary. IMO, 10 million, or roughly half of the population of the region, is a reasonable and even a conservative estimate of the number of people who died in Leopold II's Belgian Congo.

As for thinking through a place where people didn't have it quite as bad? Well, I don't know the answer to that question, in part because I don't know that we have yet even come close to unearthing enough information about what really went on in the African colonies. But Kwame Appiah's In My Father's House is an interesting book that suggests that rural African people, in some locations, really didn't have much reason to notice European conquest of the continent. So that book is worth looking into, too!

edit: fixed the citation information for the Stanley piece; thanks to /u/bearattack for noticing!