It's a rather complicated question. I would say the cycle of violence is the greatest inhibitor to moral progress.
For example, some of the French and Zionists who were tortured by the Nazis later used the same methods of tortured on Muslims (French used it on Muslim Algerians). After the Algerian Revolution (1954-62), the U.S. government hired French counter-terrorist experts for Vietnam and is still using these 'enhanced interrogation' methods.
A big problem in post-colonial world is oppression. The violent of their former colonial powers made the revolutionaries violent in many cases. The many post-revolution governments emerged from this violence and now use the corrupt, oppressive methods of governance on their own people.
In war, violence between two groups escalates, and as my favorite philosopher, Albert Camus, pointed out how choosing to escalate violence demoralizes a people. For instance, rationalizing murder, according to Camus, devalues everyones life. Mouloud Feraoun, Camus's friend from the Kabyle of Algeria during the Revolution, discovered first hand the logic of a nation demoralized by war. This logic sees the murderer the just one and the murdered one the villain. In other words, strength and violence replaced progresive morality.
Also, wars tend to destroy the moderate and dissenting voices. This polarization caused by war led to Mouloud Feraoun's death by a terrorist organisation of ultra-conservative European Algerians. This group hoped to continue the war by killing the voices calling for an end to the war because knowing these European Algerians were losing land of their birth, they acted out of desperation.