Interesting conversation with many valid points being made here. However, most seem to not want to mention or only timidly suggest the other main culprit to Haiti's current state: It's own people.
Let's all be honest and agree that not all cultures are equal and some are superior to others due to many factors such as customs, mannerisms, way of life, culture, religious beliefs (in some cases). With those things in mind, it is not difficult to see that Haitians and mainly Haitians are the main culprit behind their own misery. It started with racially cleansing their population of anyone who was not black, prohibiting them from owning property, businesses and creating an ethnostate. Add to that backwards customs such as spreading disease by openly defecating in public (which many Haitians also like to do in the DR), the ruthless pillaging of their environment by cutting down all vegetation to turn into coal, their strong attachment to voodoo, the brain drain that others mentioned here and the subsequent effects of those ppl never returning to Haiti, etc., the list goes on. It is disingenous to gloss over these things and focus solely on what the French and Americans did years ago. All of the Caribbean islands were colonized/occupied at some point in their history and none today are in the dire situation that Haiti is in. And regarding the sense of entitlement that Melphis mentioned earlier, correct me if I'm wrong but my impression is that he was referring to the Haitians in DR which do, in fact, feel entitled to be in DR as the prevailing attitude amongst many Haitians to this day is that the DR rightfully belongs to them and the smear campaigns that many of them have engaged in against the DR when the government doesn't bend to their every whim regarding who is entitled to Dominican citizenship.