Lumumba and Sankara have to be the two biggest tragedies in modern African history, and both were instigated by the West (Belgium/US and France/US respectively).
While Lumumba didn't have much of a chance to do anything, Sankara did have tremendous success at improving the quality of life and the productive capabilities of his country. What's most sad - and, it feels, relevant to today's politics - is how their predecessors ruled. Mbutu (Lumumba's chief of staff who assassinated him and ruled as a dictator for subsequent decades) and Blaise Compaore (Sankara's effective chief of staff who assassinated Sankara and ruled as a dictator for the subsequent decades) both ruled viciously and cartoonishly corruptly, but they consolidated support by trading left-wing economic populism for right-wing cultural populism. Both opened up their countries to foreign exploitation and reversed the socialistic and Third Worldist policies of their predecessors, but they smoothed it over (especially in the case of Mbutu) with cultural nationalism. Of course, colonizer countries like the US, Belgium, and France could give two shits if third world countries want to put up green, red, and yellow national symbols so long as they sell out their resources.
Mbutu is gone, but I still hold out hope that someday Compaore will be extradited to Burkina Faso and executed, preferably by means that offend international law.