There are so many countries there that it's impossible to come up with a single POD for all of them. I do have some ideas for a few, however:
Zimbabwe:
Joshua Nkomo and ZAPU leads the country instead of Robert Mugabe and ZANU. Even if he was as bad as Mugabe (which I frankly doubt) he'll die in 1999, therefore ruling Zimbabwe for "just" 19 years instead of almost 30.
Burkina Faso:
Thomas Sankara isn't overthrown. He was far from perfect, and his flaws would likely become more pronounced over the years (as with any dictator), but he'd be better than Blaise Compaoré.
South Africa: Jan Smuts' United Party wins the
1948 election. Could apartheid (which already existed, and had for decades) be a bit weaker as a result? Calling in
@Marius since he undoubtedly knows infinitely more about this than I do.
Congo:
Patrice Lumumba isn't captured, escapes to Stanleyville and, from there, overthrows Mobutu. He'd almost certainly become a dictator, but at least he wouldn't regularly travel to Paris in a Concorde. Right?
Tanzania, Kenya and Uganda: The proposed
East African Federation becomes a reality in the 1960s instead of being dropped.
Ethiopia: Haile Selassie is overthrown in the
1960 coup attempt. With a younger and more liberal monarch in charge, the Ethiopian Empire survives and the Derg is averted.
Sudan: Find a way for Khartoum to let go of the south earlier, averting
decades of civil war.
Nigeria: The
1966 coup doesn't happen. Can this avert the
Biafra War?